1

CHAPTER 1

1. INTRODUCTION

The coordination chemistry of any transition metal seems to be a

complicated function that involves numerous variables. Understanding and predicting

the results of the reactions involving transition metal is an ultimate goal in inorganic

chemistry. Metal coordination complexes have a wide variety of technological and

industrial application ranging from catalysis to anticancer drugs. In these compounds

the metal atom itself may have a number of roles, based on its coordination geometry,

oxidation state and magnetic electronic and photochemical behaviours. Schiff bases

are an important class of ligands in coordination chemistry and their complexing

ability containing different donor atoms are widely reported.1-5

Medicinal inorganic

chemistry as a discipline is considered to have boosted with the discovery of the

anticancer properties of cisplatin. Thus the application of inorganic chemistry to

medicine is a rapidly developing field, and novel therapeutic and diagnostic metal

complexes are now having an impact on medicinal practice.6-8

There are significant

structural differences between ruthenium and platinum-based antitumor drugs; yet

ruthenium based drugs could be suitable alternatives to cis-platin and carbo-platin.9-10

With the new emerging fields of science viz.; genetic engineering molecular biology,

cell biology, nanoscience, biotechnology, magnetic resonance imaging bioinformatics

etc., and the recognition of drug receptor theory, the drug development programme

has been considerably boasted. The intellectual ability of the chemist plays a pivotal

role in the development of new bioactive molecules. The primary task of the chemist

is to prepare specific new molecules that can lead more efficiently to useful drug

discovery. This may be considered broadly in terms of two types of investigational

activities which include:

2

(A) Exploration of leads involving the search for a new compounds; and

(B) Exploitation that requires the assessment, improvement and extension of the

compounds. From the practical view point it is the latter area where in rational

approaches to drug designs have been most productive with fruitful results.

With the advent of greater understanding of physiological mechanisms, it is

now possible to rationally design drugs. This rational approach to new drug

discovery takes into account the sites for drug action.

Over recent years a great deal of interest in synthesis and characterisation

of transition metal complexes of Schiff base ligand have been developed. The

preparation of a new ligand was perhaps the most important step in the development

of metal complexes which exhibit unique properties and novel reactivity. Since the

electron donor and electron acceptor properties of the ligand, structural function

groups and the position of the ligand in the coordination sphere together with the

reactivity of coordination compounds may be the factor for different studies.11-13

Their

interest stems from the ease with which they can be synthesized, due to their

versatility and wide range of complexing ability. Owing to large variety of

coordination geometries, coordination number and modes of interaction with their

ligands, metal complexes give access to different field of pathways in cancer

treatment than do organic compounds. The discovery of the anticancer properties of

cisplatin in the 1960s was a breakthrough event as far as interest in metal complexes

was concerned.14,15

Since then a tremendous number of novel metal complexes have

been synthesized and evaluated to find species with better anticancer properties, lower

toxic side effects, and less tumor resistance to cisplatin.16-22

Moreover, metal

complexes of biologically important ligands are sometimes more effective than the

free ligand. Schiff bases are potential anticancer drugs and when administered as their

3

metal complexes, the anticancer activity of these complexes is enhanced in

comparison to the free ligand. Schiff base complexes have remained an important and

popular area of research due to their simple synthesis, versatility and diverse range of

applications. The coordination chemistry of any transition metal seems to be a

complicated function that involves numerous variables. Complexes of acyclic

precursor were studied. The complex formed with the acyclic ligand appeared to

contain ligands coordinated to the metal centre. The synthesis and structural

investigations of Schiff base and their metal complexes are of considerable centre of

attension because of their potentially beneficial pharmacological properties and a

wide variation in their mode of bonding. The pronounced biological activity from

sulpha drugs has led to considerable interest in their coordination chemistry. To

achieve an appropriate balance between the electronic and steric environment around

the metal and in order to control their activity, stability and chemoselectivity, many of

these noval metal complexes have been envolved with specific ligands. Schiff base

complexes of transition metal have played a prominent role in the development of

coordination chemistry. Several Schiff base containing polyfunctional groups offer

many practical advantages and unique structural environment for complexation. The

metal complexes of transition element with heterocyclic ligands, especially those

containing nitrogen and sulphur have diverse applications in various fields including

biology and antiherbicidal activities of thioamide ligands and its metal complexes are

well known and get more attraction recently. Sulphur and nitrogen donor ligands are

also used as powerful pesticides. The well documented biological activities of

heterocyclic ligands as well as their metal complexes have attracted much attension

over the years. A numbers of heterocyclic compounds are well known and such

activities have often been related to their chelating abilities towards one more

4

essential trace metal ions. Being fascinated by significant biological implications of

transition metal complexes of various Schiff bases. There have been several crucial

experiments carried out ingeniously with respect to earlier investigations; it is

proposed to carry out systematic reactions of some platinum metal complexes with the

following ligands for present study-

Schiff bases derived from isatin and various sulpha drugs

Schiff bases derived from sulpha drugs and various aldehydes

Schiff bases derived from substituted isatin and dithiooxamide

Schiff bases derived from isonicotinoyl hydrazide and various aldehydes/

ketones

Schiff bases derived from substituted mercaptotriazoles and pyridine-2-

carboxaldehyde/ thiophene-2-carboxaldehyde

Schiff base complexes used as drugs

Schiff base complexes have remained an important and popular area of

research due to their simple synthesis, versatility and diverse range of applications.

The Schiff base transition metal complexes have been extensively studied in recent

years owing to their pharmacological properties.23-30

Substantial cytotoxic effects of

transition metal complexes containing Schiff base were examined on several neuronal

cell lines. It is well known fact that N, S and O donor atoms play a prominent key role

in the coordination of metal at the activity sites of neumerous metallobiomolecules.

Many investigations have proved that binding of drugs to a metallo-element enhances

its activity and in some cases complex possess even more healing properties than the

parent drugs. Metal complexes offer a platform for the design of noval therapeutic

compounds. Taking into account the highly desirable attributes of this type of ligands,

5

vast families of bidentate, tetradentate Schiff base ligated complexes, of wide

applicability as catalysts in numerous organic reactions, have been studied.

Scope of the present investigations

Schiff bases of a large class of organic compound containing the

azomethine group (HC=N), many chemotherapeutically important sulpha drugs like

sulphadiazine, sulphamerazine etc. The metal complexes derived from sulpha drug

and many of their complexes exhibit a wide range of biological activity. Several

reports on Schiff base complexes of metal derived from sulpha drugs. The

condensation product of sulphadiazine with aldehydes its derivatives gives biological

activity increases with complexation. The Schiff base and their metal complexes

having wide range of biological property. The Schiff base metal complexes show

more antibacterial, antifungal and antiviral activity than the individual Schiff base.

The reactivity, specificity and a number of applications in industry, agriculture and

medicine, continue to provide the necessary impetus to the study of Schiff base

complexes with transition and inner transition metals.

In the present context a brief relevant survey of literature on Schiff

base ligand and their metal complexes showed that more work on some mixed ligand

complexes to be done, even complexes are available in the literature. In view of the

above facts it was considered worthwhile to synthesize a variety of mixed ligand

Schiff base metal complexes.

6

1.1. Chemistry of ruthenium:

Like the other metals of the platinum group, ruthenium is inert to most

chemicals. Ruthenium is used for wear-resistant electrical contacts and the production

of thick-film resistors. A minor application of ruthenium is its use in some

platinum alloys.

Ruthenium forms a variety of coordination complexes. Examples are the many

pentammine derivatives [Ru(NH3)5L]n+

which often exist in both Ru(II) and Ru(III).

Perhaps it is known that ruthenium is a rare transition metal belonging to the platinum

group of the periodic table ruthenium having electronic configuration [Kr]4d7 5s

1 and

forms compounds in the oxidation states of ranging from 0 to +8 and -2. The most

prevalent precursor is ruthenium trichloride, a red solid is purely defined chemically

but versatile synthetically. Ruthenium centered complexes are being researched for

possible anticancer properties. Ruthenium is a versatile catalyst. In particular

ruthenium coordination compounds have shown promising application as anticancer

agents and may leads to the development of improved ruthenium chemotherapeutic

7

drugs. The reactivity of ruthenium complexes with nucleic acids and their constituents

is reviewed. A brief survey of the antitumor activity of ruthenium complexes.

Attempts to incorporate ruthenium into pharmaceutical agents have typically followed

two avenues of approach. Early studies were directed toward ruthenium–containing

chemotherapeutic agents and more recently workers have begun to explore the

possibility of using ruthenium for diagnostic organ imaging. While ruthenium

complexes have shown promise along both directions, there has been only one clinical

trial of a ruthenium compound, which involved RuCl3 for radio imaging tumours.

The chemistry of ruthenium is currently receiving a lot of attention,

primarily because of the fascinating electron transfer and energy transfer properties

displayed by the complexes of this metal. Ruthenium offers a wide range of oxidation

states and the reactivities of the ruthenium complexes depend on the stability and

interconvertibility of these oxidation states, which, in turn, depend on the nature of the

ligands bound to the metal.

Application of ruthenium

* Many different ruthenium compounds have been tested for their anticancer

properties, without enough investigation into their mode(s) of action. New ruthenium-

based compounds with fewer and less severe side effects, could replace longstanding

platinum-based anticancer drugs.

* Although they have a reputation as being unstable compounds, better known for

spontaneous combustion than therapeutic effects, some ruthenium organometallics

have displayed high water and air stability and an interesting spectrum of anticancer

activity.

8

* Arguably the most successful ruthenium organometallic anticancer complexes have

been the so-called 'RAPTA' complexes. RAPTA complexes are characterised by the

presence of a facially-coordinated aromatic ring (which is relatively hydrophobic) and

a PTA (1,3,5-triaza-7-phosphaadamantane) ligand (which is highly water soluble).

* Ruthenium's properties are well suited towards pharmacological applications. It can

access a range of oxidation states (II, III and IV) under physiologically relevant

conditions.

* Ruthenium compounds are being researched for use in a number of developing solar

energy technologies. The use of Ruthenium has been developed to produce advanced

high temperature super alloys suitable for aircraft jet engine turbine blades.

* Ruthenium 106 is used in the treatment of eye melanomas.

1.2. Chemistry of Rhodium

Rhodium is a so-called noble metal, resistant to corrosion, found in

platinum- or nickel ores together with the other members of the platinum group

metals. Rhodium chemistry languished for two decades. In the 1960s four disparate

lines of research suddenly burgeoned, making the chemistry of the element one of the

most active research areas of the past two decades. Rhodium is also used as catalyst

for control of exhaust emission in car (automobile) industry and in the form of

9

phosphine complexes. The analyses of rhodium in urban air born particulate matter

are challenging. Since these new pollutants are expected to increase in the

environment in proportion to the increase in the number of car fitted with catalytic

converters. These elements partially leave the surface of the catalyst during it’s as a

result of poorly known processes, including thermal and mechanical abrasion of the

catalyst and are spread and bioaccumulation the environment. This new technology

removes the automotive emission of pollutants. Rhodium supported on alumina has

been found to be superior to ruthenium, platinum and palladium in the catalytic

hydrogenation of benzene, a similar catalyst is suitable for the hydrogenation of

aromatic and heterocyclic compounds at room temperatures. Rhodium is used in large

scale in the formation of acetic acid (Monsanto process). Recent studies suggest that

their activity may bear analogy to that of cisplatin by binding to adjacent guanines on

DNA.

Application of rhodium

* Rhodium is used as a plating metal in jewellery production to enhance the whiteness

of white gold.

* Rhodium nanoparticles and nanopowders provide ultra-high surface area which

nanotechnology research and recent experiments demonstrate function to create new

and unique properties and benefits.

* The primary use of rhodium, however, is for catalytic converters in automobiles,

airplanes, buses, forklifts, trucks and other types of equipment running on engines.

* Rhodium is also available in soluble forms including chlorides, nitrates and acetates.

These compounds can be manufactured as solutions at specified stoichiometries.

10

1.3. Chemistry of iridium

The most important iridium compounds in use are the salts and acids it

forms with chlorine, though iridium also forms a number of organometallic

compounds used in industrial catalysis and in research. Iridium metal is employed

when high corrosion resistance at high temperatures is needed, as in high-end spark

plugs, crucibles for recrystallization of semiconductors at high temperatures and

electrodes for the production of chlorine in the chloralkali process. Iridium

radioisotopes are used in some radioisotope thermoelectric generators.

Application of iridium

* Iridium(III) complexes in intracellular sensing for ions and small molecules, gene-

delivery, and cancer cell detection.

* Iridium(III) complexes as anticancer drugs and cellular imaging reagents.

* Iridium complexes show the best photophysical properties: they have high quantum

yields, very long lifetimes and possess easily tunable emissions throughout the visible

range. On the other hand, Iridium is very expensive and scarcely available.

11

The variable oxidation states, coordination numbers and stereochemistries of

ruthenium(III), rhodium(III) and iridium(III) are summarized in Table 1.I, Table 1.II

and Table 1.III, respectively.

1.4. Biological applications

1. In Schiff bases metal complexes, the environment at the coordination center

can be modified by all attaching different substituents to the ligands and a

useful range of steric and electronic properties essential for the fine tuning of

structure and reactivity can thus be provided.

2. Schiff bases complexes of ruthenium are used as catalyst in the synthesis of

quantity polymers.

3. Schiff bases can accomodate different metal centers involving various

coordination modes allowing successful synthesis of homo and heterometallic

complexes with varied stereochemistry.

4. A number of research groups are activity engaged in developing new

therapeutic agents and DNA probe from transition metal Schiff base

complexes.

12

Table: 1.I. Oxidation States and Stereochemistries of Ruthenium

Oxidation

State

Coordination

number

Stereochemistry Examples

Ru-II

; d10

4 Tetrahedral [Ru(CO)4]2-

Ru0; d

8 5 Trigonal

bipyramidal

[Ru(CO)5]

RuI; d

7 6 Octahedral [n5-C5H5Ru(CO)2]2

RuII; d

6 4

5

6

10

Tetrahedral

Square pyramidal

Octahedral

Sandwich

[RuH{N(SiMe3)2}(PPh3)2]

[RuCl2(PPh3)3]

[Ru(CN)6]4-

[Ru(η5-C5H5)2]

RuIII

; d5

6 Octahedral [RuCl6]3-

RuIV

; d4

6 Octahedral KRuF6 or

[RuF6]-

RuV; d

3 6 Octahedral [RuCl6]

3-

RuVI

; d2

4 Tetrahedral [RuO4]2-

RuVII

; d1

4 Tetrahedral [RuO4]-

RuVIII

; d0

4 Tetrahedral [RuO4]

13

Table: 1.II. Oxidation States and Stereochemistries of Rhodium

Oxidation

State

Coordination

Number

Stereochemistry Examples

Rh-I; d

10 4 Tetrahedral [Rh(CO)4]

-

Rh0; d

9 6 Octahedral [Rh4(CO)12]

RhI; d

8 3

4

5

Planar

T-shaped

Square planar

Trigonal

bipyramidal

[RhCl(PCy3)2]

[Rh(PPh3)3]+

[RhCl(PPh3)3]

[RhH(PF3)4]

RhII; d

7 4

5

6

Square planar

Square pyramidal

Octahedral

[RhCl2{P(o-MeC6H4)3}2]

[Rh2(O2CMe)4]

[Rh2(O2CMe)4(H2O)2]

RhIII

; d6

5

6

Square planar

Octahedral

[RhI2Me(PPh3)2]

[RhCl6]3-

RhIV

; d5

6 Octahedral [RhCl6]2-

RhV; d

4 6 Octahedral [RhF6]

-

RhVI

; d3

6 Octahedral [RhF6]

14

Table: 1.III. Oxidation States and Stereochemistries of Iridium

Oxidation

State

Coordination

Number

Stereochemistry Examples

Ir-I; d

10 4 Tetrahedral [Ir(CO)3(PPh3)]

-

Ir 0

; d9

6 Octahedral [Ir4(CO)12]

Ir I; d

8 4

5

Square planar

Trigonal bipyramidal

[Ir(CO)Cl(PPh3)2]

[Ir(CO)H(PPh3)3]

Ir III

; d6

5

6

Trigonal bipyramidal

Octahedral

[IrH3(PR3)2]

[IrCl6]3-

Ir IV

; d5

6 Octahedral [IrCl6]2-

Ir V

; d4

6

7

Octahedral

Pentagonal

bipyramidal

CsIrF6

[IrH5(PEt2Ph)2]

Ir VI

; d3

6 Octahedral [IrF6]

15

1.5. References

1. G. Wilkinson, R. D. Gillard and J. A. McCleverty(Ed.) “Comprehensive

Coordination Chemistry”, Pergamon, Oxford, 1987.

2. J. A. McCleverty and T. J. Meyer, “Comprehensive Coordination Chemistry

II, From Biology to Nanotechnology” Elsevier, Amsterdam, 2003.

3. F. A. Cotton, G. Wilkinson, C. A. Murillo and M. Bochmann, “Advanced

Inorganic Chemistry” 6th

Edn., John Wiley and Sons, Inc., 1999.

4. C. R. Samy and S. Radhey, Indian J. Chem., 35 A, 1, 1996.

5. X. Shen, Q. L. C. Yang and Xie, Synth. React. Inorg. Met. Org. Chem., 26,

1135, 1996.

6. I. Kostova, Recent patents on Anti-Cancer Drug Discovery, 1, 1, 2006.

7. C. S. Allardyce and P. J. Dyson, Platinum Metals Rev., 45, 62, 2001.

8. A. S. Abu-Surrah and M. Kettunen, curr. Med. Chem., 13, 1337, 2006.

9. M. J. Clarke. Coord. Chem Rev., 23, 209, 2003.

10. C. X. Zhang and S. J. Lippard, Current Opinion in Chem. Bio., 7, 481, 2003.

11. F. Lions and F. K. V. Martin, J. Am. Chem. Soc., 82, 2733, 1960.

12. N. N. Greenwood and A. Earnshaw, “Chemistry of Elements”, Pergamon,

1985.

13. M. Gerloch and E. C. Constable, “Transition Metal Chemistry”, VCH,

Weinheim, 1994.

14. B. Rosenberg, L. Van Camp and T. Krigas, Nature 205, 698, 1965.

15. E. Wong and C. M. Giandomenico, Chem. Rev., 9, 2451, 1999.

16. M. J. Clark, F. Zhu and D. R. Frasca, Chem. Rev., 9, 2511, 1999.

17. Z. Guo and P. J. Sadler, Angew Chem., Int Ed 11,1512, 1999.

16

18. C. S. Allardyce, A. Dorcier, C. Scolaro and P. J. Dyson, Appl. Organomet.

Chem., 19, 1, 2005.

19. Z. Guo, P. J. Sadler and A. G. Sykes, Adv. Inorg. Chem., 49, 183, 1999.

20. C. Di, V. Milacic, M. Frezza and Q. Ping Dou, Curr. Pharm. Des., 7, 777,

2009.

21. P. C. A. Bruijnincx and P. J. Sadler, Curr. Opin. Chem. Biol., 2, 197, 2008.

22. P. J. Dyson and G. Sava, Dalton Trans., 16, 1929, 2006.

23. C. Y. Lo, H. Guo, J. J. Lian, F. M. Shan and R. S. Liu, J. Org. Chem., 67,

3930, 2002.

24. A. A. Danopoulos, S. Winston and W. B. Mother well, Chem. Commun., 34,

1376, 2002.

25. T. Ando, M. Kamigatio and M. Sawamoto, Micromol., 33, 5825, 2000.

26. A. Dijksman, A. M. Ganzalez, A. M. Payeras, I. W. C. E. Arends and R. A.

Sheldon, J. Am. Chem. Soc., 123, 6826, 2002.

27. G. B. W. L. Lithart, R. W. Meijer and M. P. Hulshof, Tetrahedron Lett., 44,

1507, 2003.

28. B. K. Keppler, M. R. Berger, T. Klenner and M. E. Heim, Adv. Drug. Res. 19,

243, 1990.

29. Z. H. Chohan, A. Munawar and C. T. Supuran, Metal Based Drugs, 8, 137,

2001.

30. A. Srivastava, N. K. Singh and S. M. Singh, Biometals, 16, 311, 2003.

17

CHAPTER 2

The new direction of interest in new enhanced present article particular

attention is devoted to the progress made in the development of synthesis procedures

for the preparation of the mono and dinuclear ruthenium(III), rhodium(III) and

iridium(III) complexes with nitrogen, oxygen and sulphur donor atoms with their

structural aspects and physicochemical properties.

2.1. Complexes of ruthenium(III), rhodium(III) and iridium(III) with nitrogen

donor ligands

(i) Complexes with amines and polyamines

Group 9 metal complexes based on iridium and rhodium have recently

arisen as fascinating potential alternatives to existing platinum and ruthenium

metallodrugs. While long regarded as chemically inert, studies over the past few years

have demonstrated that the reactivity and biological activity of iridium and rhodium

complexes may be unlocked by a suitable choice of auxiliary ligands. In addition,

group 9 metal centers have received increased popularity for the construction of

kinetically inert organometallic scaffolds as target-selective protein or enzyme

inhibitors. In this review, we summarize the recent strategies that have been utilized

for the design and development of bioactive iridium and rhodium complexes (I).1

O

OH

C NM

Cl

M = Rh(III), Ir(III)

C

(I)

18

[Ru(NH3)6]3+

is colourless and is prepared2 usually by the oxidation of

[Ru(NH3)6]2+

. Oxidizing agents that have been used include hydrazine hydrochloride,3

Na2[PtCl6], Na[AuCl4], acidified NO2

- salts,

4 Br2 in the presence of NaBr

5 and Br2

vaspour.6

Heating of [RuCI(NH3)5]Cl2 with hydrazine hydrochloride7 or treatment of

[Ru(NH3)5(OH2)]2+

with hydrazoic acid8 also gives [Ru(NH3)6]

3+. The single crystal

X-ray structures of [Ru(NH3)6]X3 (X = BF4-, C1

-)9,10

confirm an octahedral geometry

for ruthenium(III) with Ru-N = 2.104 A˚ for the BF4- salt.

9 [Ru(NH3)6]

3+ like

[Ru(NH3)6]2+

, participates in outer-sphere electron transfer reactions, a range of such

reactions involving the reduction of [Ru(NH3)6]3+

having been reported. [Ru(NH3)6]3+

quenches the excited state [Ru(bipy)3]2+

and has been suggested as a possible oxidant

in related redox systems.11

[Ru(NH3)6]3+

forms a range of mixed valent salts with

[Ru(CN)6]4-

, [Fe(CN)6]4-

and [Fe(CN)5L]3-

(L = CO, DMSO, pz, py, imid)12,13

which

show outer-sphere intervalence charge transfer bands in the visible-near IR region.

Treatment of [RuCl(NH3)5]2+

with Ag(O2CCF3), followed by zinc

amalgam reduction and addition of amine yields [Ru(L)(NH3)5]2+

(L =

cyclohexylamine, benzylamine, methylamine).14

Oxidation of these complexes with

Br2 produces the corresponding ruthenium(III) species [Ru(L)(NH3)5]3+

.

Since the introduction of cisplatin to oncology in 1978,

Platinum(II) and Palladium(II) compounds have been intensively studied with a view

to develop the improved anticancer agents. Polynuclear polyamine complexes, in

particular, have attracted special attention, since they were found to yield DNA

adducts not available to conventional drugs (through long-distance intra and

interstrand cross-links) and to often circumvent acquired cisplatin resistance.

Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly

regulated by their structural characteristics, which renders this series of compounds

19

worth investigating and their synthesis being carefully tailored in order to develop

third-generation drugs coupling an increased spectrum of activity to a lower toxicity.

The present paper addresses the latest developments in the design of novel antitumor

agents based on platinum and palladium, particularly polynuclear chelates with

variable length aliphatic polyamines as bridging ligands, highlighting the close

relationship between their structural preferences and cytotoxic ability. In particular,

studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate

the structure-activity relationships (SARs) ruling anticancer activity (II) and (III).

M = Pt or Pd; N = coordinating amine ligand(s); X = leaving group (chloride or

carboxylate); Y = axial ligands, for Pt(IV) complexes (chloride, hydroxyl, or

carboxylate); L = variable length alkyl diamine linker).

(III)

Schematic representation of mono and polynuclear

(II)

20

The mechanisms of oxidative ligand dehydrogenation in high-valent

ruthenium hexaamine complexes of bidentate 1,2-ethanediamine(en) and tridentate

1,1,1-tris(aminomethyl)ethane(tame) are elucidated in detail. In basic aqueous

solution, [Ru(III)(tame)2]3+

undergoes rapid initial deprotonation. The

disproportionation to ruthenium(II) and ruthenium(IV) has been recognized in such

systems, the complexity of the paths has not been realized previously, the surprising

variation in the rates of the intramolecular redox reaction (from days to milliseconds)

is now dissected and understood. Other facets of the intramolecular redox reaction are

also analyzed.15

Some ruthenium(II/ III) compounds containing polyamine ligands have been

synthesized and characterized by elemental analysis, IR, UV-Vis, and electrospray

ionization mass spectrometry (ESI-MS). The structures of cis-

[Ru(III)(imcyclen)Cl2(PF6)] and fac-[Ru(III)Cl3(tach)] have been determined by X-

ray crystallography (imcyclen = 1,4,7,10-tetraazacyclododeca-1-ene and tach = cis,

cis-1,3,5-triaminocyclohexane). The cytotoxicity of six ruthenium compounds has

been studied. The water-soluble compound cis-[Ru(cyclen)Cl2]Cl (cyclen = 1,4,7,10-

tetraazacyclododecane) was found to possess remarkable antiproliferative activity in

vitro against human cancer cell lines, HeLa, HepG2 and HL-60; with IC50 value of

39.2, 54.9 and 41.2 μM, respectively, while it is less cytotoxic to fibroblast cells.

Moreover, this complex can induce S-phase arrest in HeLa cells. However, this

compound is unstable in aqueous media. The result indicates that this complex

exhibits strong anti-proliferative activity towards human cancer cell lines; however, it

is also toxic to non-cancerous cell lines.16

The amines and polyamines form numerous complexes with ruthenium(III)

and rhodium(III) which have been studied extensively. [Ru(NH3)6]3+

is a colourless

21

and is prepared by the oxidation of [Ru(NH3)6]2+

. The oxidizing agents which have

been used includes hydrazine hydrochloride, Na2[PtCl6], Na[AuCl4], acidified NO2-

salts, Br2 and Br2 vapours. Heating of [RuCl(NH3)5]Cl2 with hydrazine hydrochloride,

or treatment of [RuCl(NH3)5(OH2)]2+

with hrdazoic acid also gives [Ru(NH3)6]3+

.

[Ru(NH3)6]3+

, like [Ru(NH3)6]2+

, participates in outer sphere electron transfer

reactions, a range of such reactions involving the reduction of [Ru(NH3)6]3+

have

been reported. [Ru(NH3)6]3+

quenches the excited states [Ru(bipy)3]2+

and has also

suggested as a possible oxidant in related redox systems.17

[Ru(NH3)6]3+

forms a

range of mixed valent salts with [Ru(CN)6]4-

, [Fe(CN)6]4-

, which show outer sphere

intervalence charge transfer bands in the visible near IR region.

Oxidation of amine complexes like [Ru(L)(NH3)5]2+

(L = cyclohexamine,

bezylamine, methylamine) with Br2 produces the corresponding ruthenium(III)

species [Ru(L)(NH3)5]3+

. [Ru(L)(NH3)5]3+

and [Ru(L)2(NH3)4]3+

(L = pyridine, N-

methypyrazine, 3 and 4-RCO pyridine; R = OMe, NH2, OH ) have been prepared by

silver(I) or Cerium(IV ) oxidation of the corresponding ruthenium(II) complexes. The

preparation of [Ru(L)(NH3)5]3+

by air oxidation of [Ru(L)(NH3)5]2+

( L = imidazole,

1-methylimidazole, 4-methylimidazole, 3, 5-dimethylimidazole, benzimidazole) has

also been reported,18-20

with the formation of [RuCl(NH3)4(Imid)]2+

as a side product.

The single X-ray crystal of [Ru(NH3)5pz]3+

was prepared5

by PbO2 oxidation of

[Ru(NH3)5pz]2+

. The interaction of ruthenium(III) with biologically active ligand has

been studied in complexes [Ru(L)(NH3)5]3+

(L = guanine, xanthine, hypoxanthine,

cytidine, adenosine, histidine).21-24

The structures of [Ru(L)(NH3)5]Cl3 (L =

hypoxanthine, 7-methlhypoxanthine) (IV) and (V) have been determined.25

[Ru(L)2(NH3)2]3+

and [Ru(L-L)(NH3)4]3+

may be prepared by chemical or

electrochemical oxidation of ruthenium(II) analogues and are found to be strong

22

oxidizing agents. Reduction of [Ru(terpy)(bipy)(NH3)3+

, [Ru(bipy)2(NH3)2]3+

,

[Ru(terpy)(NH3)3+

with [Fe(OH2)6]2+

has been reported and are related to Marcus

theory.26,27

HN

N

N

HN

O

Ru(NH3)5

3+

Ru(NH3)5

3+

HN

NN

HN

O

(IV) (V)

Ruthenium(III) is a very good π-acceptor. This is demonstrated by the rate of

hydrolysis of free and coordinated nitrites.28

Binuclear complexes of ruthenium(III)

pentammine with 4,4-dithiopyridine as the bridging ligand provides the first clear

example of the great efficiency of S-S bridge in conducting electrons.29

The base

hydrolysis of [Ru(NH3)5Cl]2+

is 106 times greater than acid hydrolysis as for the case

for cobalt(III) complexes, but not for chromium(III) and for rhodium(III)

complexes.30

The achiral oxidation of [Ru(NH3)6]Cl3 gives rise to an intensely

coloured solutions first reported by Joly in 1892 and known as the “ruthenium red”. A

diamagnetic red complex has been isolated in the presence of strong reducing agent as

titanium(III) and assigned as follows:

[(NH3)5RuIII

–O_Ru

IV (NH3)4–O–Ru

III(NH3)5]

6+

23

Ruthenium red has been used as a cytological stain for over a century, it exhibits

remarkable immunosuppressant activity.31

Complexes of the form [Ru(NH3)5X]n+

have been studied and restudied for

many years and the work continues, firmly bounded to rhodium(III) the five ammines

are thermally inert, leaving the sixth site for ligand substitution forms.

[Ru(NH3)5Cl]Cl2, initially prepared by Vanqulin and Clause32-33

but most modern

references are to the methods of the Johnson and Basolo34

or Wilkinson and co-

workers. Monodentate amines other than NH3 also form complexes with rhodium(III).

Edwards and co-workers prepared35

and then characterized complexes of the

form [Rh(Az)3X3], [Rh(Az)4X2]+, [Rh(Az)5X]

2+, [Rh(Az)6X]

3+, [Rh(NH3)5Az]

3+ and

[Rh(Az)3 (H2O)2(OH)]2+

, where Az = aziridine (azacyclo-propan), NH(C2H4) and X =

halide. These are prepared by direct reaction of RhCl3∙3H2O with aziridine where

aziridine act as a simple monodentate ligand.

Werner first reported that the [Rh(en)3]Cl3 salts formed when hydrated

ethylenediamine reacts with Na[RhCl6] and Jeager36-37

showed that it could be formed

when 50% en/ H2O reacts with RhCl3∙3H2O. Wilkinson and coworkers and Gasbol

have taken advantage of catalytic properties of ethanol to prepare [Rh(en)3]3+

by

reacting out RhCl3∙3H2O with ethylenediamine in aqueous ethanol. One of the more

unusual pentammine rhodium(III) complexes was reported by Wieghardt,38

who

treated the monodentate oxalatopentammine rhodium(III) cation with [Co2(µ-

OH)3(NH3)L]3-

to generate the [Co2Rh]5+

trimer isolated as the bromide salt (VI).

24

Rh(H3N)5 O

C

O

CH

O

O Co

Co

O

H

O

H

5+

(VI)

For rhodium(III) cationic species with NH3 and other amine ligands are known

generally of the type [ML6]3+

, [ML5X]2+

and [ML4X2]+, they are usually made from

the aqueous solution of RhCl3. The complex [Rh(NH3)4Cl2]Cl is also known as the

trans complex.39

The ethylenediamine complex [Rh(en)3]3+

was among the first six coordinated

complex to be resolved into their optical antimers by Werner40

in 1912. The diamines

series is represented by Na3[Rh(NH3)2(S2O3)3]- in which one thiosulphato group is

presumably bidentate cis and trans-pyH [Rh-py2Cl4], pyH[Rhpy2Br4]. Monoamines

are confined to red K2[RhNH3Cl5] and (pyH)2-[RhpyBr5] which are not very stable.

41

On heating of an alkaline solution of the [Rh(NH3)5Cl]Cl2 in an autoclave at 170˚C,

amorphous Rh(OH)3∙xNH3∙yH2O was formed. The structure of this consists of

coordination octahedral.42

The yield and the values of x and y depends on the

concentration of the [Rh(NH3)5Cl]Cl2. The structure consists of joined coordination

octahedral. Photolysis of [Rh(NH3)5(N3)]2-

can be used to generated

[Rh(NH3)5(NH2Cl)]3+

or the NH2OH analog. Structure exists as an octahedral.43

A

series of similar compounds inspired by the above precursors, have been successfully

used in the formation of mononuclear complexes.

25

(ii) Complexes with pyridine, bipyridine and 1, 10-phenanthroline

Complexes of the type [RuL3]3+

can be prepared by chemical or

electrochemical oxidation of [RuL3]3+

(where L = 2,2’-bipy, 3,3’-(Me)2bipy, 1,10-

phen, 2,9- (Me)2Phen, 4,7-(ph)2phen, 2. 2-Biquinoline, 3,3’-biquinoline, 2,2’-

bipyrazine) or as a product in the oxidative quenching of excited state [RuL3]2+

. The

oxidation of [Ru(bipy)3]2+

by PbO, Ti, Cl2 and Ce has been reported.44,45

Treatment of

[H(TMSO)][trans-RuCl4(TMSO)2] with 2,2’-bipyridine(bpy) in ethanol at room

temperature resulted in an unknown mer-[RuCl3(TMSO)(bpy)] and cis-

[RuCl2(TMSO)4] (TMSO = tetramethylenesulfoxide). Octahedral structure

suggested46

out by various studies including X-ray.

The ESR spectrum of [Ru(bipy)3]3+

is consistent with a Ruthenium(III) d5

configuration. [RuCl3(bipy)OH2] can be prepared47

by reductio of the [RuCl4(bipy)]

in H2O and ethanol or by refluxing RuCl3 with an aqueous HCl and bipy for several

days.48

Treatment of [Ru(NO)2 py4] with HX yields [RuX(NO)py4]2+

(X = Cl, Br),

with X = ClO-4 [Ru (OH) (NO)py4]

2+ is obtained,

49 Further structure of trans-

[RuCl(NO)py4]2+

was observed (VII).

Ru

N

N

Cl

N

N N

O

(VII)

26

Further one electron electrochemical reduction of this complex generates [Ru

(NO)py4(OH2)]2+

again reduction of this complex yields with zinc amalgam [RuCl

(NH3)py4]+.

The complex [RuL(OH2)5]3+

( L = N-methylpyrazinium), [RuL2(OH2)4]2+

(L =

py, pz) and [Rupy4(OH2)2]2+

can be isolated50

by the reaction of L with [Ru (OH2)6]2+

.

The complexes [RuCl3L3] can be prepared51

by reaction of [RuCl2L4] with HCl (L =

py, 2, 3- and 4- methylpyridine) or by reflux of RuCl3 with L (L = Imidazole,

substituted imidazole). Reaction of 2,2’-biquinoline and (2,2’-pyridyl) quinoline(Pq)

with the RuCl3∙3H2O, Ru(DMSO)4Cl2 and RhCl3∙3H2O were investigated and

complexes were prepared52

in 1:3 metal:ligand ratio in ethanol or methanol.

Rhodium(III) containing 2-(2’-pyridy)quinoline (PQ) were prepared by the reactio of

RhCl3∙6H2O and PQ in 1:2 mole ratio followed by addition of an excess of sodium

salts to the reaction mixture. The new complexes cis-[RhX2(PQ)2]Y (VIII) (where X

= NO2-, Y = PF6

-; X = SCN

- or NO3

-, Y = Cl

-; X = Y = I

-) and cis

[Rh(N3)2(H2O)2(PQ)]PF6 were characterized by physicochemical methods.53

Ru

N

NN

Y

X

N

+

(VIII)

27

6-(2-thieny)-2,2’-bipyridine (HL) adopts tetradentate N2S2, bidentate N2 or

terdentate cyclometallated N2C bonding modes in ruthenium(III) and rhodium(III)

complexes were reported.54

Single crystal structure of [Ru(HL)(py)(Cl3)] and

[Ru(HL)2Cl][BF4]∙CH2Cl2 are reported. The former complex contains a bidentate N2-

bonded HL ligand and meridional arrangements of chlorine while the later contains

two independent HL ligands. The reaction of K2RuCL5∙H2O with

(C5H4N)P(O)(OEt)2(L) yields K[RuCl2]OP(O)(OEt)(C5H4N)2. This compound is

stable and unreactive.55

[RuL3]X5∙nH2O (L = 2,2’- bipyridine(bipy), 1,10-phenanthroline(phen), 2-(m-

tolylazo)pyridine(tap); X = ClO4, NO3) were prepared by the reaction of RuCl3∙3H2O

with [AgL2]X in the MeOH. [Rh(bipy)3](ClO4)3 was prepared from RuCl3∙3H2O and

[Ag(bipy)2]ClO4.56

The complex K[RuIII

(EDTA)(bipy)] was synthesized and

characterized. The photolytic properties of this complex were studied and its

application in photo reduction of N2 to NH3 were reported.57

Ruthenium(III) and

rhodium(III) with 3-amino-5, 6-di(2-pyridyl)-1,2,4 triazine(ADPT) were prepared and

reported by Chaudhary et al.58

A series of mixed valance compounds Na3[EDTAH] [RuIII

LFeII(CN)5], where

L = pyrazine, 4,4’-bipyridyl, 3’3’dimethyl-4’4’bipyridyl, trans-1,2-bis(4-

pyridyl)ethylene was synthesized and characterized by physicochemicla methods.59

Synthesis of trivalent ruthenium complexes with general formula

[Ru(L)(bpy)Cl2]. Where L = p-substituted N-phenyl derivatives of 2-carbamoyl

pyridine and bpy = 2,2’-bipyridine, have been prepared60

and characterized by X-ray

analysis.

28

Bis(2,2’–bipyridine)(salicylidene-o-aminophenol) ruthenium complex was

synthesized and characterized by elemental analyses IR and UV spectra. Three

binuclear complexes with bridging 4,4’-dipyridylamine (L) were prepared61

as

Na[(NH3)5Ru(µ-L) Fe(CN)5]2H2O, [(NH3)5Ru(µ-L)Fe(CN)5]∙5H2O and [(NH3)5Ru(µ-

L)Fe(CN)5]Br∙3H2O. The reaction of the Ru-4,4’–diMe-2,2’–(4,4’-dmbpy) carbonyl

compounds were studied by experiments and computational method.62

Ruthenium(III) complexes of tetradentate pyridyl thioazophenols were

isolated63

in their pureform. Both cis and trans isomers of the dark brown coloured

ruthenium(III) complexes, having the general formula of [Ru(L)Cl2], have been

characterized by elemental analyses, spectroscopy and X-ray crystal structure. Mono

bipyridyl compounds of Ru(4,4’-L2-2,2’bipy)Ru(CO)2Cl2 (L = H, Me, T-Bu, Cl, Br,

H2PO3, NO2) were synthesized and reported.64

A series of the general formula [(RuHbbipX)2pyz)3+

; H2bbip = 2,6-bis-(2’-

benzimidazyl)pyridine, pyz = pyrazine and X = 2,2’-bipyridine/ 1, 10-phenanthroline

have been synthesized and characterized by their elemental analysis.65

A new

preparative route of ruthenium(III) coordinated 5,6-diamino-1, 10-phenanthroline is

described which triples the isolated yields found in existign synthesis and utilizes mild

reaction condition (IX).66

N

N

NOH

NOH

(IX)

29

The reaction of ruthenium trichloride with 1,10-phenanthroline or 2,2’-

bipyridine in formic acid leads to formation of [RuCl3(CO)(phen)], and

[RuCl3(CO)(bipy)].67

X-ray crystal structure helped in understanding the geometry of

the complexes formed.

Numerous rhodium(III) complexes containing coordinated pyridine and

substituted pyridines are known but this area is dominated by the chemistry of trans-

[Rhpy4Cl2]+ cation. It was first characterized by Jorgensen.

68 The coordinational

preference of tri(2-pyridyl) methanol wiht RhCl3∙3H2O was studied. Two different

methods were employed for the synthesis69

of the same final complex in which the

ligand coordinates to rhodium ion in a symmetrical N, N’,N” fashion. The reactions of

the 2,4,6-tris(2-pyridyl)1,3,5-triazine(tptz) with RhCl3∙3H2O was studied under

different experimental conditions. This reaction in ethanol gave [Rh(tptz)Cl3]∙2H2O

whereas the bis chelate complexes [Rh(tptz)2][ClO]3∙2H2O was obtained70

in a two

step reaction in acetone.

A butadiyne linked rhodium(III) porphyrin dimer containing a coordinated 4,

4’-bipyridine guest was prepared and characterized71

by UV-visible spectra. The

interaction of rhodium(III) ions with succinimide as primary and 1,10-phenanthroline

or 2,2’-bipyridine as secondary ligands is described.72

The rhodium(III) complexes fo

new mixed thiaaza-oxa macrocycles 5-oxa-2, 8-dithia[9]-[2,9]-1,10-

phenanthrolinophane (L) containing the 1,10-phenanthroline unit was studied.73

3,6-

bis(2’-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III)

chloride and bromide to give cis-[Rh(n-dppn)2Cl2]PF6∙XH2O (n = 5,6,7,8) and cis-

[Rh(n-dppn)2Br2]BrXH2O (n = 5,7) complexes.74

30

Complexes of rhodium(III) with 2(2’-pyridyl)benzthiazole(PBT) of

composition (PBTH)2[RhCl5H2O], [Rh(PBT)2X2]X, [Rh(PBT)X2]ClO4 (X = Cl, Br, l,

NCS or NO2) have been prepared.75

Rhodium(III) complexes with polypyridyl ligand,

2,4,6-tris-(2-pyridyl)-1,3,5-triazine(tptz) (X) were prepared under various

experimental conditions.76

The structure of ligand suggested their tridentate behaviour

and X-ray structure described the geometry of the complex.

N

N

N

N

N

N

(X)

Reaction of RhCl3∙3H2O with bipy or phen in ethanol/ 2-methoxyethanol with

catalytic amounts of hydrazine gives [Rh(L-L)2Cl2]+ or [Rh(phen)2Cl2]

+ in high

yields.77

Mixed complexes of the series [Rh(bipy)n(phen)3-n]3+

(n = 0-3) have been

prepared by Crosby and Flfring78

by bipy or phen substituents of both chlorides in

[Rh(N-N)2Cl2]+ (N-N = bipy or phen). Some synthetic path by the various pyridine

complexes of rhodium(III).

Rhodium(III) was used as a templating metal center for building a catenane.

Subsequently 2, 2’-bipyridine derivative was threaded through the ring. This process

being driven by coordination to the rhodium(III) center.79

Binuclear ruthenium (II/ III)

pentammine complex bridged by 4-pyridyol isonicotinamide (isoapy) and Me, 4-

31

pyridyl isonicotinamide and their congeners were studied out.80

The synthesis and

characterization by electrochemical properties of ruthenium(III) bipyridyl complexes

[Ru(dcbpy)Cl4]- (dcbpy = 4,4’- dicarboxylic acid-2,2’-bipyridine) and [Ru(bpy) Cl3L]

(L = CH3OH, PPh3, 4,4’-bpy, CH3CN) was reported by Haukka et. al.81

Reactions of the ligands, 2,6-diacetylpyridine bis(S-

methylisothiosemicarbazone) and 2,6-diacetylpyridine bis(S-

butylisothiosemicarbazone) with ruthenium(III), rhodium(III) and iridium(III) have

been studied and their structures have been proposed based on elemental analyses,

molar conductance, magnetic moment, spectral data (IR, ¹H NMR, FAB mass) and

thermal investigations. The ligands behave as pentacoordinated and give acyclic

complexes of the general formula [M(H2L)Cl2]Cl and macrocyclic complexes,

[M(L’)Cl2]Cl∙H2O, which are formed by template condensation by using β-diketones.

Pentagonal bipyramidal geometries are observed for acyclic and macrocyclic

complexes. In both types of complexes, the ligands coordinate in their amino form.

The thermal stability and mode of decomposition of the various complexes have been

studied by TGA techniques. Conductance measurements reveal 1:1 electrolytic nature

of the complexes (XI, XII).82

32

N

N N

N

C

SNH2

R

N

C

H3C CH3

H2NS

RCl

M

Cl

Cl

(XI)

N

N N

N

C

SNR

N

C

H3C CH3

NS

RCl

M

Cl

Cl.H2O

CC

R1 R1Cl

(XII)

Pure [Ru(bipy)3]Cl2 and their derivatives83

were synthesized and

the corresponding crystals were grown by slow evaporation method. The structure of

the ruthenium complexes were explained by UV-Visible spectroscopy, H-NMR, Mass

spectrum and FT-IR. Electrical measurements were carried out on grown crystals at

various frequencies. The organometallic and coordination complexes of ruthenium

33

shows better applications compare to other transition metals. Mainly ruthenium

combined with 2,2’ bi-pyridine will have major properties. Different types ruthenium

complexes prepared by exchanging new ligand instead of one 2,2’ bi-pyridine ligand

to form [Ru(bipy)2(L)]2-

this types of complexes shows different and better properties.

The variation in properties is because of the MLCT (Metal Ligand Charge transfer).

Exchange of a single ligand from [Ru(bipy)3]2-

complexes show a big difference in

the photo catalysis, electrical and optical properties etc. The electrons transfer from

Ru2+

and the substituted ligand are the main reason for the change happened in

[Ru(bipy)3]2-

complexes. This properties of [Ru(bipy)3]2-

will depends on the structure

and properties of the substituted ligands some of the examples are given as follows

imidazol(in)-2-ylidene ruthenium complexes and Ru(Cl-phen)3(PF6)2 (where Cl-phen

= 5-Chloro-1, 10-phenanthroline) used as catalyst, ruthenium complex of [(5-amino-

1,10-phenanthroline)bis(4,4’-dicarboxylic acid-2,2’-bipyridine)] used a photo voltaic

cells. In this paper reported the synthesis of new ruthenium complexes photo voltaic

properties. In our present work, we have synthesized pure [Ru(bipy)3]Cl2 and its

derivatives [Ru(bipy)2(CH4N2O)]Cl and [Ru(bipy)2(CH4N2S)]Cl.

Novel 2-(1-substituted-1H-1,2,3-triazol-4-yl)pyridine(pytl) ligands have been

prepared by “click chemistry” and used in the preparation of heteroleptic complexes

of Ru(III) and Ir(III) with bipyridine(bpy) and phenylpyridine(ppy) ligands,

respectively, resulting in [Ru(bpy)2(pytl-R)]Cl2 and [Ir(ppy)2(pytl-R)]Cl (R = methyl,

adamantine (ada), b-cyclodextrin (bcd)). The two diastereoisomers of the iridium

complex with the appended b-cyclodextrin, [Ir-(ppy)2(pytl-bcd)]Cl, were separated.

The [Ru(bpy)2(pytl-R)]Cl2 (R = Me, ada or bcd) complexes have lower lifetimes and

quantum yields than other polypyridine complexes. In contrast, the cyclometalated

iridium complexes display rather long lifetimes and very high emission quantum

34

yields. The emission quantum yield and lifetime (F = 0.23, t = 1000 ns) of

[Ir(ppy)2(pytlada)]Cl are surprisingly enhanced in [Ir(ppy)2(pytl-bcd)]Cl (F = 0.54, t =

2800 ns). This behavior is unprecedented for a metal complex and is most likely due

to its increased rigidity and protection from water molecules as well as from dioxygen

quenching, because of the hydrophobic cavity of the bcd covalently attached to pytl.

The emissive excited state is localized on these cyclometalating ligands, as underlined

by the shift to the blue (450 nm) upon substitution with two electron withdrawing

fluorine substituents on the phenyl unit. The significant differences between the

quantum yields of the two separate diastereoisomers of [Ir(ppy)2(pytl-bcd)]Cl (0.49

vs. 0.70) are attributed to different interactions of the chiral cyclodextrin substituent

with the D and L isomers of the metal complex.84

Four different poly(pyridine) complexes of ruthenium, viz.

RuII(trpy)(phen)(OH2)]

2+ (1), trans-[Ru

III(2,2'bpy)2(OH2)(OH)]

2+ (2),

[(2,2'bpy)2(OH)RuIII

ORuIII

(OH)(2,2'bpy)2]4+

(3) and [RuII(4,4'bpy)(NH3)5]

2+ (4)

(2,2'bpy = 2,2'-bipyridine, 4,4'bpy = 4,4'-bipyridine, trpy = 2,2',2''-terpyridine, phen =

1,10-phenanthroline) were tested as non-physiological charge mediators of second-

generation' glucose biosensors. The membranes for these biosensors were prepared by

casting anionic carboxymethylated β-cyclodextrin polymer films (β-CDPA) directly

onto the platinum or glassy carbon (GC) disk electrodes. Simultaneously, glucose

oxidase (GOD) was immobilized in the films by covalent bonding and the ruthenium

complexes were incorporated both by inclusion in the β-CD molecular cavities and by

ion exchange at the fixed carboxymethyl cation-exchange sites. The leakage of the

mediator from the polymer has been minimized by adopting a suitable pre-treatment

procedure. The biosensors catalytic activities increased in the order 1<2<3<4, as

established by linear sweep voltammetry. In case of complexes 2–4, the enzymatic

35

glucose oxidation was mediated by the Ru(III) complexes at their redox potentials.

However, this oxidation was mediated by oxygen in case of complex 1 where

H2O2 was detected as the reaction product. The effectiveness of the mediators used in

the presence of oxygen has been estimated using Pt and GC supports. The redox

potential of the mediator does not depend on the support used, while the oxidation of

H2O2 proceeds on GC at much higher positive potentials than on Pt. The sensitivity

and the linear concentration range of the biosensor studied varied significantly. For

complex 4, which forms stable inclusion complex with β-CD, the biosensor sensitivity

was the highest and equal to 7.2 µA mM–1

cm–2

, detectability was as low as 1 mM,

but the linear concentration range was limited only to 4 mM. In contrast, for

complexes 2 and 3 the sensitivity was 0.4 and 3.2 µA mM–1

cm–2

, while the linear

concentration range extended up to at least 24 and 14 mM glucose, respectively. Even

though some common interfering substances, such as ascorbate, paracetamol or urea,

are oxidized at potentials close to those of the ruthenium(III) complex redox couples,

their electro-oxidation currents at physiological concentrations are insignificant

compared to those due to the biocatalytic oxidation of glucose.85

Some ruthenium(III) complexes with aryl-azo 2,4-pentanedione as co-

ligands (L1H-L

3H2) have been synthesized and characterized spectroscopically IR,

1H

NMR, UV/ Vis, ESR, conductimetric) along with elemental analysis and FAB-mass

data. Their luminescent and redox properties have been studied. The antibacterial,

anti-HIV and antitmnour activities have also been reported.86

A novel synthetic methodology that involves the “disassembly” of

diruthenium(III) tetracarboxylates using the modestly π-acidic bidentate 2,2′-

bipyridine and 1,10-phenanthroline ligands and their substituted derivatives as

disassembling agents was exploited to generate, in high yield, heteroleptic bis-

36

diamine-mono-carboxylate-Ru(III) complexes. The reactions proceed so that these

heteroleptic complexes are only formed when steric hindrance is introduced directly

adjacent to the binding nitrogen atoms otherwise the homoleptic tris-diamine

ruthenium(III) complexes are formed exclusively. Two novel heteroleptic complexes

have been synthesized in high yield, namely [Ru(η2-O2CCH3)(6,6′-Me2-2,2′-

bipy)2](PF6) and [Ru(η2-O2CCH3)(2,9-Me2-1,10-phen)2](PF6). Both complexes have

been characterized using X-ray crystallography, elemental analysis, IR, NMR and

UV–visible spectroscopy and cyclic voltammetry.87

A number of complexes of trivalent iridium with 1:10-phenanthroline(phen)

have been isolated. The complexes are of three types: (a) tris-chelated,

[Ir(phen)3]X3∙nH2O (X = Cl, Br, I, ClO4); (b) bis-chelated, [Ir(phen)2X2]X∙nH2O (X =

Cl, Br); (c) those containing a bis-chelated cation and a mono-chelated anion,

[Ir(phen)2X2][Ir(phen)X4]∙nH2O (X = Cl, Br, I). The compounds of were obtained in

cis and trans isomeric forms.88

Possible preparative routes to trans di halogeno bis (1,10 phenanthroline)

iridium(III) cations have been investigated and it is concluded that the existence of

these ions is doubtful. Convenient syntheses89

of cis-Ir(phen)X2∙X (X = Br, I) and also

of [phenH][Ir(phen)Br4] are noted. It was found that pure products resulted only when

the iridium was supplied to the reaction as iridium(IV). The reaction between

solutions of [Ir(phen)X4]- (X = Cl, Br) in concentrated oxidising acids and pure nitric

oxide was noted and is suggested as a sensitive colour test for [Ir(phen)X4]-.

37

(iii) Complexes with imidazole, benzimidazole and guanidibenzimidazole

The title compound mer-trichloro bis(1-methylimidazole)(DMSO)

ruthenium(III) and 4-ethylpyridium trans-(4-ethylpyridine)(DMSO)

tertrachlororuhenate(III) were synthesized.90

The synthesis and characterization of three cis-[Ru(bpy)2(L)2] (bpy = 2, 2’-

bipyridine) (L = monodentate ligand 1-methylimidazole) is reported.91

2-

methylimidazole(2-Melm) reacts with ruthenium trichloride in aqueous acidic

ethanolic medium to give92

(2-MelmH)2[RuCl5(2-Melm)] and (2-MelmH)[RuCl4(2-

Melm)2].

Complexes of RuCl3 with biologically important benzimidazole derivatives of

2-(hydroxymethyl)benzimidazole, 2-(1-mercaptoethyl)benzimidazole and 2,2’-

dibenzimidazole were synthesized by reacting RuCl3 and respective ligands in 1:3

molar ratio.93

(HL)2[RuLCl5]∙H2O (L = benzimidazole) (HL1)2[RuL

1Cl5]∙H2O [L

1 = 2-

methyl benzimidazole] and (HL2∙HCl)[RuL

2(HCl)Cl5]2H2O [L

2 = 2-

benzimidazolylacetonitrile) were synthesized and characterized.94

A novel dinuclear ruthenium compound, [(tpy)Ru(tmbimbpyH4)Ru(tpy)]ClO-4

was synthesis to introduce a new proton-induced molecular system where tpy = 2,

2’:6’2”-terpyridine and tmbimbpy H4 = 2,6’:2’6”-tetra(4,5-dimethyl benzimidazole-2-

yl)-4, 4’-bipyridine are reported.95

Mononuclear and binuclear ruthenium(III)

polypyridyl complexes containing 2, 6-bis(2’-benzimidazyl) pyridine as ligand of

formula [Ru(Hbbip)-XCl]

+, [Ru(Hbbip)(X)2]

2+ and [Ru(Hbbip)X]2[pyz]

3+, H2bbip = 2,

6-bis(2’-benzimidazyl) pyridine was prepared and characterized.96

38

The synthesis of trans-[RuL4X2]+

{L = N-alkylimidazoles(N-Rlm), [R = Me,

Et, Pr, Bu], 4(6)-hydroxypyridine (4(6)-hydPm), X = Cl-

or Br-} is achieved by

general catalytic method using ethanol.97

The synthesis and characterization of

coordination compounds of ruthenium with di and trichloroguanidinopyrimidines are

described.98

These compounds were found octahedral.

Rhodium trichloride is found to form complexes of the types

(LH)2RhCl5L]∙2H2O, (L’H)RhCl4L’2]∙2H2O, (L’H)RhCl4L’2], where L = 2-

methylimidazole (2-Melm), 1, 2-dimethylimidazole (1, 2-Me2Im); L’ = imidazole

(Im), 1-n-butylimidazole (1-n-Bulm). The compounds have been characterization99

by

spectral properties and elemental analyses.

Lee et. al.100

has worked on the synthesis of a new compound of rhodium as

[Rh(pik)2Cl2]Cl (pik is 2-pyridyl N-methyl-2-imidazolyl ketone). Complexes of the

form [Rh(RBig)2Cl2]Cl (RBig = N1-(p-chlorophenyl), N

1-phenyl, N

1-(O-tolyl), N

5-

isopropylbiguanide) have been prepared in which the biguanide act as N-N

bidentate.101

Smart design and efficient synthesis of benzimidazole ruthenium, iridium and

rhodium cyclometalated complexes are reported with promising cytotoxic activity

against HT29, T47D, A2780 and A2780cisR cancer cell lines. Their apoptosis,

accumulation, cell cycle arrest, protein binding and DNA binding effects are also

discussed (XIII).102

39

N

N X

R1

M

L2L1

R2

O

O

Me

M = Ru(III), Ir(III), Rh(III)

(XIII)

Cyclometalated rhodium(III) and iridium(III) complexes (1–4) of

two Schiff base ligands L1 and L2 with the general formula [M(ppy)2(Ln)]Cl {M =

Rh, Ir; ppy = 2-phenylpyridine; n = 1, 2; L = Schiff base ligand} have been

synthesized. The new ligands and the complexes have been characterized with

spectroscopic techniques. Electrochemistry of the complexes revealed anodic

behavior, corresponding to an M(III) to M(IV) oxidation. The X-ray crystal structures

of complexes 2 and 4 have also been determined to interpret the coordination

behavior of the complexes. Photophysical study shows that all the complexes display

fluorescence at room temperature with quantum yield of about 3×10−2

to 5×10−2

. The

electronic absorption spectra of all the complexes fit well with the computational

studies. Cellular imaging studies were done with the newly synthesized complexes.

To the best of our knowledge, this is the first report of organometallic complexes of

rhodium(III) and iridium(III) with Schiff base ligands explored for cellular imaging.

Emphasis of this work lies on the structural features, photophysical behavior, cellular

uptake and imaging of the fluorescent transition metal complexes.103

The electrochemical behavior of the binuclear platinum(III–III) complexes

[Pt2(C4H3N2S)4X2] (C4H3N2S−

= pyrimidine-2-thionate; X−

= Cl−, Br

−, I

−) have been

40

studied by cyclic voltammetry and in situ spectroelectrochemistry in an acetonitrile–

tetrabutylammonium tetrafluoroborate solvent-electrolyte couple. An irreversible

metal based reduction appears during the cathodic scan for each of the three

complexes. The changes in UV–Vis spectra observed in-situ during the reductive

electrolysis indicate that all three complexes give the same product, [Pt2(C4H3N2S)4],

with a Pt(II)–Pt(II) system. The changes in the reduction potentials of the complexes

on changing the axial ligands are interpreted by the changes in the energy of the

LUMO level, which is determined by the degree of Iƒ and I-interactions of the axial

halide ligands with the metal atoms. DFT (B3LYP/ LanL2DZ) calculations support

our experimental data.104

In the reaction of N,N′-methylenebis[(4S,5R)-4-methoxycarbonyl-5-

methyloxazolidine] (1) with CuCl2 or RuCl3 in alcoholic solvents novel complexes,

bis[(4S,5R)-4-methoxycarbonyl-5-methyl-1,3-oxazolidine]copper(II) dichloride (2)

and bis [(4S,5R)-4-methoxycarbonyl-5-methyl-2-oxazoline]-(4S,5R)-4-

methoxycarbonyl-5-methyl-1,3-oxazolidineruthenium(III) trichloride (3),

respectively, were isolated and fully characterized by X-ray crystallography. In these

reactions, which occurred under mild conditions, ligand 1 was cleaved at the bridging

aminal position and degraded to (4S,5R)-4-methoxycarbonyl-5-methyl-1,3-

oxazolidine 5. The trigonal bipyramidal Cu complex 3 contains two such oxazolidine

ligands coordinated in different ways. One is bonded in a monodentate fashion via the

nitrogen atom of the five-membered ring, the other binds as a bidentate ligand,

additionally using the carbonyl oxygen of the ester group. In the octahedral Ru

complex 4 there are one oxazolidine ligand 5 and two oxazoline ligands 6. Thus, in

the synthesis of 4 the carbon atom between oxygen and nitrogen in the oxazolidine

41

ring was partly oxidized from the half-aminal status to the carboxamide status

(XIV).105

O

N

MeOOC

Ru

HCl

Cl

Cl

Me

O

N

COOMe

Me

O

NMeOOH2C

Me

(XIV)

Until recently, rhodium(III) and particularly iridium(III) complexes were

generally considered as being unlikely candidates for anticancer agents owing to the

typical kinetic inertness of their transition metal centres. Systematic studies on the

cellular impact of a range of octahedral rhodium(III) complexes containing

polypyridyl and other aromatic chelates have now, however, demonstrated that high

cytotoxicity in cancer cells and in certain cases promising relative tolerance by

healthy cells can be achieved by judicious selection of the remaining ligands. Current

knowledge on the biological properties of rhodium(III) and iridium(III) compounds is

reviewed in this article, with particular emphasis being placed on design strategies

and on their solution behaviour, DNA binding preferences, structure activity

relationships and apoptosis induction in both adhesive and non-adhesive cells

(XV).106

42

Cl

Ir

Cl

N

N CH3

CH3

SH

Cl

CH3

OCH3

(XV)

Among the infectious illnesses designated by the World Health Organization

(WHO) as neglected tropical diseases (NTDs), four illnesses are major health

concerns in the developing world: malaria and three parasitic diseases caused by

genetically related parasites belonging to the trypanosomatid genus and kinetoplastida

order: American trypanosomiasis, human African trypanosomiasis and leishmaniasis.

This review focuses on the most relevant efforts carried out to develop ruthenium

compounds as potential agents for the treatment of these diseases. Those series of

compounds for which especial efforts have been made to modify structures

performing a sort of rational design and to identify their molecular targets and mode

of action were emphasized. Aspects related with the potentialities and perspectives of

ruthenium compounds for this particular inorganic medicinal chemistry field are also

included.107

(iv) Complexes of other nitrogen containing ligands

The first Rh(III)-RB(pz)3 (where RB(pz)3 = tripyrazolylborate anion, act as a

tridentate ligand) complexes were prepared108

by the oxidative addition of iodine to

[Rh2{RB(pz)3}(CO)3] and resulted in octahedral, monomeric complexes

[Rh{RB(pz)3}(CO)l2] [R = H, and in low yield for R = pz]. The single crystal

43

structure of trans-methyliodo{diflouro[3,3’-trimethylenedinitrato]bis(2-pentanone

oximato) borate} rhodium(III) (XVI) shows that the rhodium sits in the plane with

four nitrogen atoms with I and Me at the axial positions.109

RhN

N

N

N

O O

BF F

Me

(XVI)

Dwyer and Nyholm110

first reported the preparation of [Rh(DMG)2Cl2]- ion

(isolated as the H+salt) but his formulation was questioned by Gillard et. al.

111 Who

pointed out [Rh(DMG)2Cl2]- anion as [Rh(DMG)HDMG)Cl2]. Powell

112 has reported

the synthesis of many [Rh(DMG)2LX] complexes (L = PPh3, AsPh3, SbPh3, X = Cl,

Br, I) prepared by heating aqueous ethanolic solution of RhCl3∙3H2O, L and HDMG

in the presence of the appropriate potassium salt.

Using 3,5-dimethyl-1-(4,6’-dimethyl-2’-pyrimidyl)pyrazole(DPymPz) (XVII)

as a coordination ligand, rhodium(III) complexes of the type [Rh(DPyMPz)2X3] (X =

Cl, Br, I) have been isolated in the solid state and characterized by physicochemical

methods.113

The rhodium(III) complexes have pseudooctahedral geomety.

44

N N

N

N

CH3

H3C

H3C CH3

(XVIII)

Ruthenium(III) and rhodium(III) complexes with 1,3,5-triazine-2, 4, 6-

tiramine- N, N, N’, N’N”, N”- hexaacetate have also been prepared.114

The Schiff base octaazamacrocyclic ligands derived from primary diamines

and 3, 6-dimethyl/ diphenyl-4, 5-diazaocta-3, 5-diene-2, 7-dione, and their binuclear

complexes [M2LCl4]Cl2 [M = Cr(III), Fe(III), Co(III) or Ru(III)] and

[Mn2L(AcO)4](AcO)2 were synthesized by template condensation reactions. Attempts

to synthesize the corresponding metal free macrocyclic ligands did not prove

successful. The overall geometry and stereochemistry of these complexes were

elucidated by elemental analyses, magnetic susceptibilities, electronic spectra,

infrared spectra, molar conductance measurements, 1H NMR and thermogravimetric

analysis. All the trivalent metal ion complexes appear to be 1:2 electrolytes. An

octahedral geometry is proposed for all the complexes (XVIII).115

45

MN

N

N

N

X

X

R

R

R

NM

N

X

X

N N

R

R

R

R

R'

X2

R'

(XVIII)

A number of diruthenium(III) complexes with dinucleating ligands formed

from diaminodiphenyls and triazene-1-oxide or pyridine-2-carboxylate were

synthesized and characterized.116

Novel six coordination ruthenium complexes with

heterocyclic N complexes as ligands were prepared and used as immunosuppressive

agents.117

Novel sundianionic and neutral ruthenium(III) dimer Na2{trans-

RuCl4(Me2SO-S)}(µ-L) and [mer,cis-RuCl3(Me2SO-S)(Me2SO-S)2(µ-L)] (L =

pyrazine, pyrimidine and 4,4-bipyridine) were synthesized and characterized.118

The phthalocyanine complexes of ruthenium and ruthenium chloride are easily

prepared from phathalic anhydride and the corresponding metal salts using microwave

radiation under solvent free conditions.119

Synthesis of tris(3-

nitroformazanato)rhodium(III) chelates were reported and characterized by elemental

analyses. The coordination of these ligands occurs to N1

and N5

position and NO2

group does not take part in coordination.120

46

The synthesis and characterization of the ruthenium(III) and rhodium(III)

complexes with 1,3-diaryltriazenido [Ru(ArNNNAr)(CO)3]2, [Ru(ArNNNAr)2]2, cis-

[Ru(ArNNNAr)(CO)2], MX2[Ru(ArNNNAr)(PPh3)2 (M = Ru; X = Cl, Br) and

M(ArNNNAr)3 (M = Ru, Rh) are reported.121

Reactions of 8-hydroxy-7-quinoline

carboxaldehyde (LH) with RuCl3∙3H2O afforded [RuL3] and [RuL2ClOH2]. Reactions

of LH with RuCl3∙3H2O in presence of N-heterocyclic bases gave [RuL2Cl(py)] and

[RuL2Cl(phen)].122

Arylazo oximes act as a bidentate ligands ligands (N-N) form [Rh(N-N)3]

complexes with rhodium(III).123

Where reaction of Rh(NO3)3∙3H2O with appropriate

arylazooxime in ethanol at pH-4 leads to precipitate of fac- and mer-[Rh(N-N)3].

2.2. Complexes of ruthenium(III), rhodium(III) and iridium(III) with oxygen

donor ligands

(i) Complexes with ᵦ-diketones

A range of ketoenolate complexes [Ru(III)L3] have been prepared124

by the

reaction of blue ruthenium(III) chloride with the corresponding diketone under basic

conditions or by ligand exchange with the [Ru(acac)3] (XIX). The single crystal X-ray

structure of [Ru(acac)3] shows octahedral ruthenium(III) with average Ru-O distance

of 2.0A. Ruthenium(III) compounds with -diketones containing triphenylphosphine

and triphenylarsine were prepared and characterized by various physicochemical

methods.125

47

O

O O

O

O O

Ru

(XIX)

[Ru(acac)2(cod)] can be prepared126

by treatment of RuCl3 with cod and oxalic

acid in refluxing ethanol for 2 hours followed by treatment with acetic acid, Hacac

and K2CO3. A similar route yields [Ru(acac)2(nbd)]. [Ru(acac)Cl2(OH2)2] has been

synthesized127

by reaction of RuCl3 with acac in aqueous HCl. A new mode of

binding of -diketone was established in a mononuclear complex which was obtained

as S and O donor atoms ligand. [Ru(acac)2(topd-O,S)] and binuclear [[Ru(acac)2]2(µ-

topd-O,S,O)] complex was synthesized by Hashimato et al.128

[Ru(III)(L)Cl2(PPh3)2]

and [Ru(II)(L)2(PPh3)2] and [Ru(II)(L)2(PPh3)2] (HL = benzoylacetone or

acetylacetone) were synthesized129

by reaction of [RuCl2(PPh3)3] with HL.

Synthesis of [Ru(acac)2(Ch3CN)2]ClO4 was achieved by an oxidation of

[Ru(acac)2(CHCN)2] with AgClO4 or Ce(lV) salt [Ru(acac)2L2]ClO4 (where L = py,

3-Me-py, 4-Me-py, PPh3, AsPh3, L2 = 2,2’-bipyridine or 1,10-phenanthroline (phen))

was synthesized and reported by Gupta et al.130

Ruthenium(III) containing

triphenylphosphine or triphenylarsine complexes with -diketones were prepared131

by reaction of [RuX3(EPh3)] (X = Cl or Br; E = P or As) with RCO(MeCO)Ch-Y-

CH(COR)(COMe) [R = Me or Ph, Y = (CH2)6, (CH2)10] in 2:1 ratio. Another -

diketone complex of ruthenium(III) was synthesized by a new method in high yield as

[Ru(acac)3] and is a precursor for the synthesis of [Ru(acac)2L2] (L = a neutral

48

monodentate ligand viz.MeCN, py, 3-Mepy, 4-Mepy, dmpzh (3,5-dimepyrazole) PPh3

or AsPh3, L2 = a neutral bidentate ligand viz.bipy or phen).132

Binuclear ruthenium(III) hexacoordinated low spin d5 complex as

[Ru2(acac)2L] (acac = acetylacetonate, L = dicarboxylate) were synthesized from

reaction of [Ru(acac)3] with various dicarboxylic acids.133

Synthesis of

{[(acac)2Ru]2(µ-L)} and {[(bipy)(acac)Ru]2(µ-L)} (acac = acetylacetonato, bipy =

2.2’-bipyridine) was reported by Gupta et al.134

A novel oxalate bridged binuclear

ruthenium(III) complexes {[Ru(acac)2]2(µ-oxo)} (acac-

= acetylacetonate and ox2-

=

oxalate) was prepared via selfdimerization of K[Ru(acac)2(ox)] in aqueous solution.135

Synthesis and characterization of a new ruthenium(III) complex [Ru(acac)2(mhmk)]

with coordinated -kitiminate ligands was reported136

and their geometry was

described by X-ray crystallography. The complexes were found octahedral.

Rhodium(III) compounds viz. [RhCl2(acac)(acacH)] [acacH = acetylacetone]

was isolated in high yield by reaciton of the RhCl3 with acacH. The complex is

convenient starting material for synthesis of [RhX2(acac)L2] (X = Cl or Br; L = PPh3,

AsPh3 or py), [RhX2(acac)(L-L)] (X = Cl or Br, L-L = bipy or phen).137

The synthesis of new -diketonato rhodium complex

[Rh(FcCoCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] with Fc = ferrocenyl

and R = Fc, C6H6, CH3 and CF3 are described.138

The neutral [Rh(acac)3] complex

was first prepared139

by reacting [Rh(NO3)3] with acetylacetone in an aqueous (pH4)

solution. The [Rh(hfacac)3] and [Rh(tfacac)3] (hfacac = hexafluoroacetylacetonate,

tfacac = trifluoroacetylacetonate) analogs were later prepared by similar method.140

Reaction of the dioxygen adduct of [RhCl(PPh3)3] with Hacac at room temperature in

49

benzene leads to a hydroperoxo complex of rhodium(III) identified as

[Rh(PPh3)2(COOH)Cl(acac)].

Two mononuclear mixed ligand ruthenium(III) complexes with oxalate

dianion (Ox2-

) and acetylacetonate ion (2,4-pentanedionate, acac-) as

K2[Ru(Ox)2(acac)] and K[Ru(Ox)(acac)2] were prepared141

as a candidate of a

building block.

A number of complexes of rhodium(III) and iridium(III) with para- and meta-

substituted benzeneseleninic acids are reported and characterized by spectroscopic

methods. The benzeneseleninate complexes were prepared by the reaction of the

sodium aryl-seleninate with RhCl3 and (NH4)3IrCl6. From the electronic absorption

spectra the values of the ligand field parameters were determined. The nephelauxetic

parameters are all indicative of appreciable metal-ligand covalency. The Ir spectral

data suggest that the complexes contain RSeO2−

ligands chelating the metal via the

oxygen atoms. A monomeric structure for the tris(benzeneseleninato) complexes is

suggested.142

The anthryl-substituted rhodium(III) and iridium(III) heteroleptic β-

ketoenolato derivatives of general formula [M(acac)2(anCOacac)] [acac = pentane-

2,4-dionate; anCOacac = 3-(9-anthroyl)pentane-2,4-dionate], 3 (M = Rh) and 4 (M =

Ir) and [M(acac)2(anCH2acac)] [anCH2acac = 3-(9-anthrylmethyl)pentane-2,4-

dionate], 5 (M = Rh) and 6 (M = Ir), were prepared by reacting the corresponding

tris(pentane-2,4-dionate)metal complexes, [M(acac)3], with 9-anthroyl chloride and 9-

chloromethylanthracene, respectively, under Friedel−Crafts

conditions. Complexes were characterized by elemental analysis, ion spray mass

spectrometry (IS-MS), 1H NMR and UV−vis spectroscopy. The structure was also

50

elucidated by single-crystal X-ray analysis. When excited at 365 nm, result to be

poorly luminescent compounds; while the free diketone, i.e., 3-(9-

anthrylmethyl)pentane-2,4-dione1, whose structure was established also by single-

crystal X-ray analysis, results to be a strongly light emitting molecule. The study of

the electrochemical behavior of ligands as well as of the corresponding tris-

acetylacetonates of rhodium(III) and iridium(III) allows a satisfactory interpretation

of their electrode process mechanism and gives information about the location of the

redox sites along with the thermodynamic and kinetic characterization of the

corresponding redox processes. All data are in agreement with the hypothesis that the

quenching of the anthracene fluorescence, observed for compounds 3-6, can be due to

an intramolecular electron transfer process between the anthryl moiety and the metal β

ketoenolato component. Moreover, a study was carried out of the redox behavior of

the dyads under chemical activation. The one-electron oxidation of compounds by

thallium(III) trifluoroacetate leads to the formation of the corresponding cation

radicals, whose highly resolved X-band EPR spectra were fully interpreted by

computer simulation as well as by semiempirical and DFT calculations of spin density

distribution (XX).143

X

O

O

O

OM

O

O

X = CO or CH2; M = Rh(III) or Ir(III)

(XX)

51

The anthryl-substituted rhodium(III) and iridium(III) heteroleptic beta-

ketoenolato derivatives of general formula [M(acac)2(anCOacac)] [acac = pentane-

2,4-dionate; anCOacac = 3-(9-anthroyl)pentane-2,4-dionate], 3 (M = Rh) and 4 (M =

Ir), and [M(acac)2(anCH2acac)] [anCH2acac = 3-(9-anthrylmethyl)pentane-2,4-

dionate], 5 (M = Rh) and 6 (M = Ir), were prepared by reacting the corresponding

tris(pentane-2,4-dionate) metal complexes, [M(acac)(3)], with 9-anthroyl chloride and

9-chloromethylanthracene, respectively, under Friedel-Crafts conditions. 3-6 were

characterized by elemental analysis, ion spray mass spectrometry (IS-MS), 1H NMR,

and UV-vis spectroscopy. The structure of 3 was also elucidated by single-crystal X-

ray analysis.144

Novel rhodium, iridium, and ruthenium half-sandwich complexes containing

(N,N)-bound picolinamide ligands have been prepared for use as anticancer agents.

The complexes show promising cytotoxicities, with the presence, position and

number of halides having a significant effect on the corresponding IC50 values. One

ruthenium complex was found to be more cytotoxic than cisplatin on HT-29 and

MCF-7 cells after 5 days and 1 hour, respectively and it remains active with MCF-7

cells even under hypoxic conditions, making it a promising candidate for in vivo

studies.145

The aim of this study was to investigate cellular response to several

ruthenium(III), chromium(III) and rhodium(III) compounds carrying bidentate beta-

diketonato ligands: [(acac)-acetylacetonate ligand, (tfac)-trifluoroacetylacetonate

ligand]. Cell sensitivity studies were performed on several cell lines (A2780,

cisplatin-sensitive and -resistant U2-OS and U2-OS/ Pt, HeLa, B16) using growth-

inhibition assay. Effect of intracellular GSH depletion on cell sensitivity to the agents

was analyzed in A2780 cells. Flow cytometry was used to assess apoptosis by

52

Annexin-V-FITC/ PI staining, and to analyze induction of caspase-3 activity. Possible

DNA binding/ damaging affinity was investigated, by inductively coupled mass

spectrometry and by 14C-thymidine/ 3H-uridine incorporation assay. Cell sensitivity

studies showed that the pattern of sensitivity to Ru(tfac)3 complex of the two

cisplatin-sensitive/ resistant osteosarcoma cell lines, U2-OS and U2-OS/ Pt, was

similar to that of A2780 cells (72 h exposure), with the IC50 being around 40

microM. The growth-inhibitory effect of Ru(acac)3 ranged over 100 microM, while

chromium(III) and rhodium(III) complexes were completely devoid of antitumor

action in vitro. Ru(tfac)3 exhibited strong potential for apoptosis induction on A2780

cells (up to 40%) and caused cell cycle arrest in the S phase as well as decrease of the

percent of G1 and G2 cells. Ru(acac)3-induced apoptosis was slightly higher than

10%, whereas activation of caspase-3 in HeLa cells was moderate. DNA binding

study revealed that only Cr(acac)3 was capable of binding DNA, while chromium(III)

and ruthenium(III) compounds possess potential to inhibit DNA/ RNA synthesis. In

conclusion, only ruthenium(III) complexes showed potential for antitumor action.146

The reaction of the Schiff bases (obtained by condensing isatin with o-

aminophenol/ o-aminothiophenol/ o-aminobenzoic acid) with [RuX3(EPh3)3] (where

X = Cl/ Br; E = P/ As) in benzene afforded new, air-stable ruthenium(III) complexes

of the general formula [Ru(L)X(EPh3)2] (L = dianion of tridentate Schiff bases). In all

these reactions, the Schiff base ligand replaces one triphenylphosphine/

triphenylarsine and two chlorides/ bromides from the ruthenium precursors.147

A group of six ruthenium(III) complexes of type [Ru(acac)(L)2]where acac =

acetylacetonate anion and L = 2-(arylazo)-4-methylphenolate anion or 1-(phenylazo)-

2-naphtholate anion have been synthesized and characterized Structural

characterization of a representative complex where L = 1-(phenylazo)-2-naphtholate

53

anion shows that the azophenolate ligands are coordinated as NO-donor ligands

forming six-membered chelate rings.148

Ruthenium, palladium and platinum complexes of 2,2,6,6-tetramethyl-3,5-

heptanedione (thd) and ruthenium tris acetylacetonate (acac) were synthesized and

studied with TG, DTA, DSC and MS methods. Thermal properties of ruthenocene

were also studied. The platinum thd complex has the highest volatility despite the

second highest molecular mass of the complex. All the complexes sublimed under

reduced pressure. Ru(acac)3 decomposed during sublimation under atmospheric

pressure of nitrogen whereas the other compounds studied sublimed also under these

conditions. Pd(thd)2 reduced under atmospheric pressure of H2/ N2 (5% H2 ) whereas

the ruthenium complexes were not reduced. The field desorption mass spectra of

complexes showed only the molecular peaks and no fragmentation occurred.149

Preparation of ruthenium(III) and rhodium(III) tris-acetylacetonates and

palladium(II) bisketoiminate (Pd(i-acac)2) under microwave irradiation using different

synthetic conditions, both in the solid-phase and in solution, was studied with precise

control of parameters. In the solid-phase systems, the preparation of the target product

was hindered. The efficiency of the microwave heating increased when liquid phases

of the reagent mixtures were used. For Pd(i-acac)2, the highest yield was achieved

under elevated temperature of the process, with the reaction time decreasing to several

minutes. A laboratory procedure for the microwave synthesis of ruthenium(III) and

rhodium(III) tris-acetylacetonates and palladium(II) bis-ketoiminate in aqueous

solutions was developed, which allowed us to obtain them in 85, 55 and 80% yields,

respectively. These yields are higher than those reported in the literature, with the

process becoming considerably less time consuming and laborious.150

54

γ-Halogenated iridium(III) acetylacetonates of the general formula

Ir(acacX)n(acac)3−n (where acacX is CH3–CO–CX–CO–CH3, acac is CH3–CO–CH–

CO–CH3, n = 1,2,3, X = F, Cl, Br, I) have been synthesized, purified and

characterized. Spectroscopic and thermogravimetric studies have been carried out, as

well as study of the relative volatility and thermal stability of the complexes. For a

series of compounds, powder X-ray diffraction studies and crystallographic

characteristics have been obtained. The structures of Ir(acac)3, Ir(acacCl)3, Ir(acacBr)3

and Ir(acacI)3 complexes have been determined.151

A range of ketoenolate complexes [Ru(III)L3] have been prepared152

by the

reaction of blue ruthenium(III) chloride with the corresponding diketone under basic

conditions or by ligand exchange with the [Ru(acac)3]. The single crystal X-ray

structure of [Ru(acac)3] show octahedral ruthenium(III) with average Ru-O distance

of 2.0 A. Ruthenium(III) compounds with ᵦ-diketones containing triphenylphosphine

and triphenylarsine were prepared and characterized by various physicochemical

methods.153

(ii) Complexes with carboxylates

Treatment of [Ru(CO)12] with carboxylic acids at reflux gives, as major

product, the insoluble polymer species [Ru(OCOR)(CO)2]n (R = Me, Et, C9H19). For

R = Me, this is also formed154

by carbonylation (1 atm) of RuCl3∙3H2O and

Na[OCOMe] in MeCOOH/ acetone at 80˚C.

Reaction of RuCl3∙3H2O with acetic acid/ acetic anhydride mixtures gives the

brown solid [Ru2(OCOMe)4Cl] and a green colour solution.155

Higher yields are

obtained if the reaction is performed in the presence of an excessof LiCl. Hydrolysis

of [Ru2(OCOMe)4Cl] affords [Ru2(OCOMe)4(OH2)2]+ whereas treatment with CsCl

55

gives Cs[Ru2(OCOMe)4Cl2] these have dimeric discrete structure.156

The reaction of

RuCl3∙3H2O with acetic acid/ acetic anhydride was believed to contain a binuclear

ruthenium acetate complex but an X-ray structure determination of its PPh3,

[RuO(OCOMe)6(PPh3)3] suggested it should be reformulated an oxo triruthenium

species.157

Treatment of [Ru3O(OCOMe)6(MeOH)3]+ with dppm or dppe gives the

binuclear cations (XXI). Where as dppm and [RuO(OCOMe)6(MeOH)3] affords two

isomers of [Ru2(OCOMe)4(dppm)2], some [Ru(OCOMe)2(dppm)2] is also produced.

Ru

PO

P

P

P

O

Ru

PO

P

P

P

O

H2

C

CH2

2+

(XXI)

The ruthenium(III) trisoxalato anion [Ru(C2O4)3]3-

was first prpeared by

Charonnat158

as its potassium salt by the reaction between K2[RuCl5(OH2)] and

K2[C2O4]. Treatment of RuO2∙3H2O with an excess of ammonium hydrogen oxalate

gives159

[NH4]3[Ru(C2O4)3]∙5H2O. The [Ru(C2O4)(OH2)4]+ ion have been reported to

exist in aqueous solution and the [Ru(C2O4)2(OH2)2]- anion has been isolated as its

sodium salt by treatment of [Ru(OCOMe)4Cl] with an aqueous Na2[C2O4] under an

oxygen atmosphere. Other oxalate complexes include various nitrosyl species such as

K2[RuCl3(C2O4)NO], K2[RuCl(C2O4)NO], K[Ru(C2O4)NO(py)],

[RuCl(C2O4)NO(py)2], the black K2[Ru(C2O4)3] from the oxidation of K3[Ru(C2O4)3]

56

with H2O2 and CS2[RuO2(C2O4)2] obtained by treatment of RuO4 with an ice cold

solutions of CS2[(C2O4)] and oxalic acid.160,161

Synthesis of trans-[RuCl2(nic)4] and trans-[RuCl2(i-nic)4] compounds where

nic = 3-pyridinecarboxylic acid were achieved162,163

by using ruthenium blue

solutions as a precursor. The preparation of two ruthenium(III) polyamino carboxylate

compounds AMD 6245 and AMD 6221 and their nitrosyl derivatives was reported by

Cameron et. al.164

and the complexes where characterized by IR and 1H NMR.

Replacement of H2O or OH ligands in [Rh2(O2-)(OH)2(H2O)n]

3+ cation by

carboxylate ions RCO2- (R = Et, Pr, Bu, Me3, glycine, L-aspartic acid and L-proline)

were studied. Two new rhodium(III) superoxo carboxylates formulated as [Rh2OS2-

](OH)(RCO2)4]n were synthesized by Olkowski et al.165

Hexadentate rhodium(III) compounds of 1,3-propanediamine-N, N-diacetic N,

N’-di-3-propionic acid as trans-(O5)-Na[Rh(1,3-pddadp)]H2O and trans-(O5O6)-

Na[Rh(1,3-pddadp)]H2O (where 1,3-pddadp = 1,3-propanediamine-N,N’-deacetate-

N,N’-di-3-propionate ion) were synthesized by Rychlewska et. al.164

[Rh(NH3)3(NO3)3] reacted with thiodiacetic acid [H2L] or Na2L to give

[RhL(NH3)3]NO3 in different crystalline forms.165

Werner et. al.166

first time prepared [Rh(Ox)3]3-

ion which has an electronic

spectrum consistent with an octahedral RhO6 chromophore. Reaction of [Rh(Ox)3]3-

in refluxing perchloric acid leads to cis-[Rh(Ox)2(H2O)2]-, subsequent substitution

lead to cis and trans isomers of [Rh(Ox)2X2]n-

(X = H2O, Cl) which have been

characterized by electronic and IR spectroscopy.167

57

Luminescent cyclometalated rhodium(III) and iridium(III) complexes of the

general formula [M(ppy)2(N (wedge)N)][PF6], with N (wedge) N = Hcmbpy = 4-

carboxy-4'-methyl-2,2'-bipyridine and M = Rh, Ir and N (wedge), N = H 2dcbpy =

4,4'-dicarboxy-2,2'-bipyridine and M = Rh, Ir, were prepared in high yields and fully

characterized. The X-ray molecular structure of the monocarboxylic iridium complex

[Ir(ppy)2(Hcmbpy)][PF6] was also determined. The photophysical properties of these

compounds were studied and showed that the photoluminescence of rhodium

complexes and iridium originates from intraligand charge-transfer (ILCT) and metal-

to-ligand charge-transfer/ ligand-centered MLCT/ LC excited states, respectively. For

comparison purposes, the mono and dicarboxylic acid ruthenium complexes

[Ru(DIP)2(Hcmbpy)][Cl]2 and [Ru(DIP)2(H2dcbpy)][Cl]2, where DIP = 4,7-diphenyl-

1,10-phenanthroline, were also prepared, whose emission is MLCT in nature.

Comparison of the photophysical behavior of these rhodium(III), iridium(III), and

ruthenium(II) complexes reveals the influence of the carboxylic groups that affect in

different ways the ILCT, MLCT, and LC states.168

Reactions of the chloride-bridged dimers [LMCl(μ-Cl)]2 (M = Rh, Ir; L = Cp*

= η5-C5Me5; M = Ru, L = η

6-p-cymene) with two mole equivalents of thiosalicylic

acid (HSC6H4CO2H, H2tsal) and excess base gives the dimeric rhodium(III),

iridium(III) and ruthenium(II) thiosalicylate complexes [LM(tsal)]2. Reaction of the

complex [Cp*RhCl2(PPh3)] with one equivalent of H2tsal and triethylamine in

dichloromethane gives a mixture of the dimer [Cp*Rh(tsal)]2 and the phosphine

complex [Cp*Rh(tsal)(PPh3)]; upon recrystallisation, pure dimer is obtained. A

single-crystal X-ray diffraction study on the rhodium and ruthenium dimers reveals

the expected thiolate-bridged M2(μ-S)2 unit. Electrospray mass spectrometry (ESMS)

is a useful technique in studying the chemistry of the thiosalicylate complexes, all

58

complexes giving strong [M+H]

+ ions. With added thiosalicylic acid, cations of the

type [(LM)2(Htsal)3]+ were detected in the mass spectra.

169

Ruthenium complexes [RuIII

(L1)(PPh3)2(Cl)] (1) and [Ru

III(L

2)(PPh3)2(Cl)] (2)

(in which L1H2 and L

2H2 are iminodiacetic acid and pyridine-2,6-dicarboxylic acid,

respectively, and H stands for a dissociable proton) derived from the ligands that

contain two carboxylate groups were synthesized and characterized. These complexes

were treated with in situ generated NO derived from acidified nitrite solution, which

afforded the formation of two {Ru–NO}6 complexes [Ru(L

1)(PPh3)2(NO)](ClO4) (1a)

and [Ru(L2)(PPh3)2(NO)](ClO4) (2a). The molecular structure of the representative

complex [Ru(L2)(PPh3)2(NO)](ClO4) (2a) was determined using X-ray

crystallography. Characterization of complexes 1a and 2a by IR and NMR

spectroscopic studies revealed the presence of {Ru–NO}6 species with S = 0 ground

state. ESI-MS data also supported the formation of 1a and 2a. Exposure to UV light

promoted rapid loss of NO from both ruthenium nitrosyls to generate

RuIII

photoproducts of the type [Ru(L)(PPh3)2(S)](ClO4) (in which S stands for

solvent). The quantum yields of NO photorelease for complexes 1a and 2a were

measured using a chemical actinometry study. The NO released in solution was

estimated using the Griess reagent and the results were compared with the data

obtained from sodium nitroprusside (SNP). A 2,2-diphenyl-1-picrylhydrazine (DPPH)

radical quenching assay was performed to estimate the amount of generated reactive

nitrogen species and reactive oxygen species under aerobic conditions during

photolysis of NO.170

The synthesis and characterization of optically active amino carboxylate

complexes of formula [(η6-arene)Ru(Aa)Cl] (arene = C6H6, C6Me6, Aa = amino

carboxylate) as well as those of the related trimers [{(η6-arene)Ru(Aa)}3][BF4]3 are

59

reported.Trimerization takes place with chiral self-recognition: only diastereomers

equally configured at the metal, RRuRRuRRu or SRuSRuSRu are detected. The crystal

structures of the complexes [(η6-C6H6)Ru(Pip)Cl] and [{(η

6-

C6Me6)Ru(Pro)}3][BF4]3 have been determined by X-ray diffraction methods. Both

types of complexes catalyse the hydrogen transfer reaction from 2-

propanol to ketones with moderate enantioselectivity (up to 68%). The enantio

differentiation achieved can be accounted for by assuming that Noyori's bifunctional

mechanism is operating.171

Reaction of [Ru(OH)(NH3)5]Cl2 with acetic anhydride followed by acid

hydrolysis and treatment with Ag+ gives [Ru(OAC)(NH3)5]

2+.172

Oxalic acid with

[Ru(OH)(NH3)5]2+

[RuCI(NH3)5]2+

affords cis-[Ru(ox)(NH3)4]+.173,174

Carboxylato

complexes can be prepared generally by treatment of [RuCI(NH3)5]2+

with

Ag(O2CCF3) followed by addition of carboxylate buffer in DMF.175

Charge transfer

bands for the complexes [Ru(O2CR)(NH3)5]2+

are observed near 300 nm and are

related to the E/ z values for reduction of the complexes.176

Ruthenium complexes [RuIII

(L1)(PPh3)2(Cl)] and [Ru

III(L

2)(PPh3)2(Cl)] (in

which L1H2 and L

2H2 are iminodiacetic acid and pyridine-2,6-dicarboxylic acid,

respectively and H stands for a dissociable proton) derived from the ligands that

contain two carboxylate groups were synthesized and characterized. These complexes

were treated with in situ generated NO derived from acidified nitrite solution, which

afforded the formation of two {Ru–NO}6 complexes [Ru(L

1)(PPh3)2(NO)](ClO4) (1a)

and [Ru(L2)(PPh3)2(NO)](ClO4). The molecular structure of the representative

complex [Ru(L2)(PPh3)2(NO)](ClO4) was determined using X-ray crystallography.

Characterization of complexes 1a and 2a by IR and NMR spectroscopic studies

revealed the presence of {Ru–NO}6 species with S = 0 ground state. ESI-MS data

60

also supported the formation of 1a and 2a. Exposure to UV light promoted rapid loss

of NO from both ruthenium nitrosyls to generate RuIII

photoproducts of the type

[Ru(L)(PPh3)2(S)](ClO4) (in which S stands for solvent). The quantum yields of NO

photo release for complexes were measured using a chemical actinometry study. The

NO released in solution was estimated using the Griess reagent and the results were

compared with the data obtained from sodium nitroprusside (SNP). A 2,2-diphenyl-1-

picrylhydrazine (DPPH) radical quenching assay was performed to estimate the

amount of generated reactive nitrogen species and reactive oxygen species under

aerobic conditions during photolysis of NO.177

The interaction of hydrated ruthenium trichloride with carboxylic acid-acid

anhydride mixtures gives crystalline complexes of formula [Ru2(OCOR)4Cl], (R =

Me, Et, nPr), where the ruthenium atoms have formal oxidation states of II and III.

These complexes have high magnetic moments over the temperature range 300-100 K

and appear to be the first spin-free complexes of ruthenium to be prepared. Other less

well defined ruthenium carboxylates are described.178

Several mononuclear and dinuclear ruthenium carbonyl acetate complexes

containing bipyridine or phenanthroline have been tested as catalysts in the

hydrogenation of alkenes, alkynes and ketones. They are active in polar solvents and

in water and the nitrogen containing ligands are unaltered at the end of the

hydrogenation.179

Under aerobic conditions, the ruthenium(II) triphenylphosphine complex

RuCl2(PPh3)3 reacts with a few ferrocene carboxylic acids in a mixture of THF and

benzene to afford ruthenium(III) (carboxylato) complexes of the type,

RuCl2(O2CR)(PPh3)2, where R = alkyl or aryl derivatives of bis(cyclopentadienyl)

61

iron, the title complexes have been confirmed through element analytical, infrared and

ESR spectral studies. Infrared spectra of the complexes suggest that the carboxylate

groups of ligands coordinate to ruthenium(III) through the two oxygen donor

atoms.180

(iii) Complexes with other oxygen donor ligands

The ruthenium complexes incorporating only nitrate, sulphate or related oxy

anion ligands are generally defined. The chemistry of heavy metal nitrates, nitrites

and dioxygen181

complexes have been reviewed. The synthesis, spectroscopic

characterization and crystal structures of [RuCl3(TMSO)2(CO)] and [H(TMSO)2]-

[RuCl4(TMSO)(CO)] were reported by Srivastava et al.182

The complexes are

prepared in the presence of carbon monoxide at ambient temperature and pressure.

The reaction of [RuBr3(CO)4] with L (L = pyridine N- oxide, PPh3) in CHCl3 yields183

the complexes [RuBr3(CO)3L].

[RuX(dioxolene)(terpy)] compounds were synthesized by Kurihara et al.184

The molecular structure of [RuCl(O2C6H2-3,5-Bu2)](terpy) and

[Ru(OAc)(O2C6H4)terpy] were determined by X-ray.

Complexes of 1,3-bis(thiomorpholino) propane with ruthenium(III) were

prepared and characterized185

by X-ray as [RhLCl2]Cl∙4H2O and [RhLCl2]PF6.

Complexes of rhodium(III) with 2-(acetylamino)benzoic acid, 2-(benzoylamino)

benzoic acid and 2-(2-aminophenylamino)-carbonyl benzoic acid give O4 kind of

linkage.186

The synthesis and characterization of rhodium(III) and ruthenium(III)

complexes of 2-(1-indazoly)benzoxazole were reported by Khan.187

62

The synthesis, spectroscopic characterization and crystal structure of

[(DMSO)2H](trans-RuCl4(DMSO)(CO)] and mer[cis-RuCl3(DMSO)2(CO)] are

reported188

with octahedral geometry. When RhCl3∙3H2O was suspended in a hot

alkaline solution of (+) 3-acetylcamphorate(+atc) for 20 hours four diastereomers of

[Rh(+atc)3] were identified by spectroscopy.189

Several complexes of DMSO ligands have been prepared190

and led to the

suggestion that [Rh(DMSO)6](BF4)3 has four O bonded and two S-bonded DMSO

ligands. An X-ray structure of the [RhCl3(DMSO)3] shows that two of the DMSO

ligands are S-bonded while the third is bonded through oxygen atom.191

The products

[RuCl3L3] (L = 2,6-Lutidine-N-Oxide,192

phosphate-N-oxide derivatives,193

8-

hydroxyquinoline-N-oxide)194

and oxygen bonded [RuCl3L2] (L = thiomorpholin-3-

one) have been prepared.

Reaction between [Ru(PPh3)3Cl2] and 3-chloroperbenzoic acid yields

[Ru(PPh3)2Cl2(O2CC6H4-3-Cl)], the carboxylate ligand is O,O0-bonded with each O-

donor trans to a Cl atom. Again starting from [Ru(PPh3)3Cl2], the complexes[Ru(PP

h3)2Cl2L] have been prepared where HL is salicylaldehyde, 2-hydroxyacetophenone

or 2-hydroxynaphthylaldehyde, each L ligand acts as an O,O0-chelate. If HL is used

in a two fold excess, ruthenium(II) productsare obtained. Although

K3[Ru(ox)3]5∙5H2O has been known since 1931, studies on the pure compound have

been few. The solid-state structure have been determined and confirms

K3[Ru(ox)3]5∙5H2O to be isomorphous with its rhodium(III) and iridium(III) analogs.

Ketonate complexes of ruthenium(III) are reported in a number of papers. The parent

complex [Ru(acac)3] has been subject to a polarized neutron diffraction study at 4.18

K, to powder neutron diffraction studies and to single-crystal structure determinations

at 293 K, 92 K and 10.5 K. The structure is disordered at all temperatures.

63

Measurements of the magnetic susceptibilities (at 2.5 K and 300 K) have been made

along different crystal axis directions and the results analyzed. An investigation of the

relationships between ionization potentials and half-wave potentials of a series of

tris(ketonate) ruthenium(III) complexes has been reported and the electrochemical

properties of [Ru(acac)3] in chloroaluminate molten salt media have been reported.

The reduced species [Ru(acac)3]- can react with AlCl4

-; reduction by bulk electrolysis

of a small amount of [Ru-(acac)3] in the melt yields[RuCl6]3-

. Treatment of

RuCl3∙xH2O with Hacac gives trans-[Ru(acac)2Cl2](the first trans-bis(acac) complex

to have been made). The complex anion isa precursor to a range of ruthenium(IV),

ruthenium(III) and Ru(II)trans-bis(acac) complexes including trans-[Ru(II)(acac)2L2]

where L¼MeCN or pyrazine (pyz); the cis analog are from direct reaction between

[Ru(acac)3] and MeCN or pyz. The reaction of [Ru(acac)3] with molten 1,3-

diaminobenzene yields complexes. Their formation involves ruthenium mediated

oxidative di and trimerization of 1,3-diaminobenzene. Structural data for [Ru(acac)3]

and [Ru(3-Bracac)3](H-3-Bracac¼3-bromopentane-2,4-dione) 560 ruthenium and

osmium: Low Oxidation States have been reported. Protonation of [RuL3](L¼acac

and derivatives) in MeCN leads to [RuL2(MeCN)2]. The ruthenium(II) complexes

[RuL2(MeCN)2] (L¼acac and derivatives) have been used as precursors to mixed

diketonate Ru(III) complexes. The mechanisms of the interconversions between the

three isomers of [Ru(acac)(tfpb)2] (Htfpb¼4,4,4-trifluoro-1-phenyl-1,3-butanedione)

have been studied in dmf at 363 K, 383 K, and 403 K. The data are consistent with a

bond-rupture mechanism through trigonal–bipyramidal intermediates. Starting from

[Ru(3-Iacac)3](H-3-Iacac¼3-iodopentane-2,4-dione), the alkyne-functionalized

complexes [Ru(3-Me3SiCCacac)3] and [Ru(3-HCCacac)3] may be prepared. The

latter has been polymerized; 1H NMR spectroscopic data are consistent with a chain-

64

like polymer and electrochemical data indicate that there isonly short-range Ru-Ru

communication. Peroxide oxidation of Na[Ru(hfac)3](Hhfac¼1,1,1,5,5,5-

hexafluoroacetylacetone) yields [Ru(hfac)3]; from either the Ru(II) or Ru(III)

complex, cis-[Ru(hfac)2(MeCN)2] can be prepared. Treatment of cis-

[Ru(acac)2(MeCN)2] with hfac gives[Ru(acac)2(hfac)], from which the ruthenium(II)

complex cis-[Ru(acac)(hfac)(MeCN)2] have been prepared. Measurementsof the

rateso f electron transfer cross-reactions between [Ru(CF3COCHCOCR)3] and

[Ru(CF3COCHCOCR)3]- (R = ¼CF3, Me, tBu, Ph, furyl, thienyl) have been made in

MeCN using stopped-flow methods. Assignment of oxidation states in quinone (Q)/

semiquinone (SQ) complexes is not straightforward. The structural and spectroscopic

characteristics of [Ru(bpy)2(DBSQ)] and [Os(bpy)2(DBCat)](DBCat¼3,5,-di-tert-

butylcatechol; SQ¼semiquinone) reveal a difference in charge distribution between

the complexes on going from ruthenium to osmium. For osmium, C-O bond lengths

of the quinone ligand are consistent with a reduced catecholate and in line with this,

near IR transitions and EPR spectroscopic data are consistent with an oxidation state.

In contrast, the Ru complex appears to be some where between Ru(II)-DBSQ and

Ru(III)-DBCat. The same mid-picture is concluded from structural data for trans-

[Ru(4-tBupy)2(DBSQ)2], although it is pointed out that the result may arise from a

crystallographic disorder of a localized Ru(III)(SQ)(Cat) species. Related systems

have also been analyzed. In [Ru(PPh3)2(DBSQ)Cl2], the structural properties of the

O,O0-donor ligand are consistent with a semiquinone formulation and, therefore,

ruthenium(III). Complexes containing both 3,5,-di-tertbutylcatechol and

tetrachlorocatechol (Cl4SQ¼semiquinone form) have also been studied and the

structure of [Ru(PPh3)2(Cl4SQ)2] have been determined; the structural parametersare

consistent with a semiquinone form of the ligand. Treatment of [Ru(PPh3)3Cl2] with

65

1-hydroxy-2,4,6,8-tetra-tert-butylphenoxazinyl radical (HphenoxSQ) gives

[Ru(PPh3)2Cl2(phenoxSQ)] or [Ru(PPh3)Cl(phenoxSQ)2] depending on the reactant

stoichiometry. Coupling between the radical and the S¼ = 1/2 Ru center in

[Ru(PPh3)2Cl2(phenoxSQ)] renders the complex diamagnetic;

[Ru(PPh3)Cl(phenoxSQ)2] is paramagnetic. The work has been extended to a number

of related complexes. Reaction of [Ru(NH3)5Cl]Cl2 and 3,4-dihydroxybenzoic acid in

NH4OH solution yields [Ru(NH3)4(diox-COO)] where diox-COO¼ 3,4-

diolatobenzoate. [Ru(NH3)4(diox-COO)] could be formulated as [Ru(III)(NH3)4(cat-

COO)] or [Ru(II)(NH3)4(SQCOO)]. Further complexes with catecholate, semiquinone

or quinone ligands are described under ruthenium(II).

2.3. Complexes of ruthenium(III), rhodium(III) and iridium(III) with sulphur

donor ligands

(i) Complexes with thiocarbamates and dithiocarbamates

Several reviews with cover the chemistry of ruthenium

dialkyldithiocarbamates have appeared in the last fifteen years.195,196

Cambi and

Malatesta197

and later Malatesta198

reported the low spin, monomeric [Ru(S2CNR2)3]

(R = Me, Et, Bun), which was prepared by reacting K2[RuCl6] with aqueous

Na[S2CNR2].

More recently compounds of this type have been prepared by the reaction of

the N[S2CNR2] with solutions of RuCl3∙3H2O. Several studies has been published for

the redox behaviour of [Ru(S2CNR2)3]. One electron reversible reduction to

[Ru(S2CNR2)3]- is observed but the one electorn oxidation is quasi reversible and the

product [Ru(S2CNR2)3]+ is unstable towards further reaction or decomposition. Earlier

studies199

had indicated that [Ru(S2CNEt2)3]+ was synthetically accessible adn aerial

66

oxidation in the presence of BF3 was reported to yield [Ru(S2CNEt2)5]BF4. Binuclear

Ru(III), cation [Ru(S2CNEt2)5] BF4 (XXII) was also formed.

Ru

SS

S

S

SRu

SS

S

S S

(XXII)

The yellow crystalline ‘Ru(S2CNR2)2CO’ (R = Me, Et) and

[Ru(S2CNR2)2(CO)2] (R = Me, PhCh2) were prepared by reaction of ethanolic

solution of ‘RuCOCl’ with Na[ S2CNR2] or tetrasubstituted thiuramdisulfied. The

related thioxanthate complex [Ru(S2CSMe)2(CO)2] is formed200

by additions of CS2

to THF solutions of Na2[Ru(CO)4], followed by the reaction with methyl iodide.

Raston and White201

revealed by X-ray that Ru(S2CNEt2)2CO has the dimeric

structure (XXIII) in the solid state. This compound can also be formed by UV

irradiation.

Ru

CoS

S

S

SRu

SS

S

S Co

(XXIII)

67

The monothiocarbamate cations [Ru(SOCY)(PMe2Ph)4]PF6 (Y = OEt, NMe2)

can be prepared by treating [RuH(PMe2Ph)5]PF6 with COS in EtOH or EtOH/ NHMe2

respectively.202

Sokolov et al.203

synthesized the complex [Ru2(µ-

pyS)3(PyS)2](CF3SO3) by reaction of Ru2(OAc)4Cl with PySH with complete

substitution of acetate ligands and oxidized it to give a bioctahedral dimer [Ru2(µ-

pyS)3(PyS)2](CF3SO3).

Several new hexacoordinated ruthenium(III) complexes [RuX2(EPh3)2(LL’)]

(X = Cl, Br, E = P or As) (Where LL’ = morpholinedithiocarboxylate,

piperidinedithiocarboxylate) were synthesized where heterocyclic dithiocarbamates

behave as uninegetive bidentate (SS) chelating ligand.

The complexes of the type M(HMICdt)2or3, where M = Ru(III) and Rh(III) and

H(MICdt)- = hexamethyleneiminecarbodithiolate have been prepared.

204 Their

structure has been established by elemental analyses and magnetic measurements.

Synthesis of the [MIV

(RR’dtc)3]+/ M

III(RR’dtc)3] and [M

IV(Et2dsc)3]

+/ M(III)(Et2dsc)3,

(M = Rh, dtc = dithiocarbamate, dsc = diselenocarbamate) observed and reported.205

The N, N-disubstituted dithiocarbamate ligand (R2CNS2-) stabilizes high

oxidation states of the first row transition metals and BF3 oxidation of

[Rh(Me2NCS2)3] was reported to lead to rhodium(IV) cation. Hendrickson et al.206

reported this product actually as the dimeric cation [Rh2(Me2NCS2)5]+. The cation

consist of a [Rh(Me2NCS2)2]+ unit coordinated to an octahedral [Rh(Me2NCS2)3] unit

through two mutually cis sulphur atoms. The complex [Rh(dtc)3] (dtc = Et2NCS2-)

were prepared by heating an aqueous solution of RhCl3∙3H2O with sodium salt of the

ligands, the addition of a small amount of ethanol to the solution allows the reaction

to proceed at room temperature.207

68

A series of metal dithiocarboxylates (RCS2-) including [Rh(dtb)3],

(NH4)[Rh(dtb)2Cl2] and [Rh(dtpa)3] has been characterized.208

Because of the strong

intraligand bands, characteristics of dithiocarboxylates was expected to be in

octahedral environment with rhodium(III). If RhCl3∙3H2O is used [Rh(dtb)3] forms

but if [RhCl6]3-

react under virtually the same condition the product is [Rh(dtb)2Cl2]-.

N-methyl-o-ethylthiocarbamate(MTC) reacted with rhodium trichloride to form

[Rh(MTC)3X3] (X = Cl, Br, I), [RhCl2(MTC)2] and [RhCl2(MTC)], which have been

characterized209

by electronic, IR and 1H NMR spectra. Ligands act as a sulphur

donors towards the rhodium atom [RhCl3(MTC)2] contains bridging Rh-Cl bonds. In

dimethyl sulphoxide all complexes decomposes with progressive displacement of the

ligand.

The complexes trans-[RuCl(S2CNR2)2(NO)] (R2 = Me, Et, MePh, MeEt) were

prepared by the reaction of [RuCl3NO] with two equivalents fo Na[S2CNR2]. A series

of cis-[RuX(S2CNR2)2NO] (X = Cl, Br, I, NO2, SCN, N3NCO, F) have been

synthesized210

by treatment of the trans chloro compounds with either HX or Agx.

Rhodium(III) complexes with cyclic dithiocarbamates and their methyl esters

and thiuram disulfide have been reported.211

The complexes of ruthenium(III) and

rhodium(III) with piperazine dithiocabamate (Pzdtc) and of ruthenium(III) and

rhodium(III) with piperazine bisdithiocarbamate (Pzbdtc) have been prepared and

characterized on the basis elemental and spectral analyses.212

The complexes of ruthenium(III) and rhodium(III) with N-ethyl-N-m-

tolyldithiocarbamato have been prepared in aqueous medium and characterized.213

All

the dithiocarbamate ligands act as a bidentate ligand. Except the ruthenium(III)

complexes, all the other complexes are diamagnetic. The complexes of type ML3 (M

69

= Ru and Rh; HL = cyclopentyldithiocarbamic acid, cycloheptyldithiocarbamic acid)

have been prepeared215

and characterized by magnetic moment and IR and UV

spectra.

The [M(pmdtc)(pip)(OH)2H2O] (M = Ru and Rh; Hpmdtc =

pentamethylenedithiocarbamic acid; pip = piperidine), have been prepared and

characterized.216

The complex were found octahedral rhodium(III) dithiocarbamate

complexes of the types M(Rdtc)3 and M(Rdtc)2’ (M = Rh(III), Rdtc = 2-3-4-

methylpiperidine dithocarbamate) have been prepared and characterized.217

The preparation of a series of [Ru(III)(tacn)(eta2-dtc)(eta-dtc)][PF6] (tacn =

1,4,7-triazacyclononane; dtc = dimethyldithiocarbamate, diethyldithiocarbamate,

pyrrolidinedithiocarbamate, l-prolinedithiocarbamate, l-prolinemethyl ester

dithiocarbamate, l-N-methylisoleucinedithiocarbamate) complexes 5 is described.

Complex 5 reacts with NO to form the ruthenium nitrosyl complex 12. A series of

[Ru(III)(tacn)(pyc)Cl][PF6] (pyc = 2-pyridinecarboxylic acid, 2,4- and 2,6-

pyridinecarboxylic acid) complexes, 14-16, were prepared along with

[Ru(III)(tacn)(mida)][PF6] (mida = N-methyliminodiacetic acid), 13 and

[Ru(III)(Hnota)Cl], 17, (Hnota = 1-acetic acid-4,7-bismethylcarboxylate-1,4,7-

triazacyclononane). Complexes 5-17 were evaluated for use as NO scavengers in an

in vitro assay using RAW264 murine macrophage cells. [Ru(III)(tacn)(eta2-dtc)(eta-

dtc)][PF(6)] complexes 5-11 are very efficient NO scavengers in this assay.218

Pyridinecarboxylic acid complexes, 14-16, were prepared along with

[Ru(III)(tacn)(mida)][PF6] (mida = N-methyliminodiacetic acid), 13 and

[Ru(III)(Hnota)Cl], 17 (Hnota = 1-acetic acid-4,7-bismethylcarboxylate-1,4,7-

triazacyclononane). Complexes 5-17 were evaluated for use as NO scavengers in an

70

in vitro assay using RAW264 murine macrophage cells. [Ru(III)(tacn)(eta2-dtc)(eta-

dtc)][PF6] complexes 5-11 are very efficient NO scavengers in this assay.219

The preparation of a series of [Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)]

(tacn = 1,4,7-triazacyclononane; dtc = dimethyldithiocarbamate,

diethyldithiocarbamate, pyrrolidinedithiocarbamate, l-prolinedithiocarbamate, l-

prolinemethyl ester dithiocarbamate, l-N-methylisoleucinedithiocarbamate)

complexes, 5-11, is described. Complex 5 reacts with NO to form the ruthenium

nitrosyl complex 12. A series of [Ru(III)(tacn)(pyc)Cl][PF(6)] (pyc = 2-

pyridinecarboxylic acid, 2,4- and 2,6-pyridinecarboxylic acid) complexes, 14-16,

were prepared along with [Ru(III)(tacn)(mida)][PF(6)] (mida = N-

methyliminodiacetic acid), 13, and [Ru(III)(Hnota)Cl], 17, (Hnota = 1-acetic acid-4,7-

bismethylcarboxylate-1,4,7-triazacyclononane). Complexes 5-17 were evaluated for

use as NO scavengers in an in vitro assay using RAW264 murine macrophage cells.

[Ru(III)(tacn)(eta(2)-dtc)(eta(1)-dtc)][PF(6)] complexes 5-11 are very efficient NO

scavengers in this assay.220

Reactions of the chloride-bridged dimers [LMCl(μ-Cl)]₂ (M = Rh, Ir; L = Cp*

= η⁵-C₅Me₅; M = Ru, L = η⁶-p-cymene) with two mole equivalents of thiosalicylic

acid (HSC₆H₄CO₂H, H₂tsal) and excess base gives the dimeric rhodium(III),

iridium(III) and ruthenium(II) thiosalicylate complexes [LM(tsal)]₂. Reaction of the

complex [Cp*RhCl₂(PPh₂)] with one equivalent of H₂tsal and triethylamine in

dichloromethane gives a mixture of the dimer [Cp*Rh(tsal)]₂ and the phosphine

complex [Cp*Rh(tsal)(PPh₃)]; upon recrystallisation, pure dimer is obtained. A

single-crystal X-ray diffraction study on the rhodium and ruthenium dimers reveals

the expected thiolate-bridged M₂(μ-S)₂ unit. Electrospray mass spectrometry (ESMS)

71

is a useful technique in studying the chemistry of the thiosalicylate complexes, all

complexes giving strong [M+H]⁺ ions. With added thiosalicylic acid, cations of the

type [(LM)₂(Htsal)₃]⁺ were detected in the mass spectra.221

New ruthenium(III), rhodium(III) and Palladium(II) complexes with the

ambident ligand 2-(3-pyridylmethyliminomethyl) phenol have been synthesized and

characterized by electronic absorption and IR spectroscopy, 1H NMR and elemental

analysis and electrophoresis methods. The synthesis conditions and the nature of the

metal turn out to have an effect on the coordination mode of the ligand in the resulting

complexes. The existence of the intramolecular hydrogen bond in the ligand molecule

is favorable for its coordination in the molecular form to the complex-forming

metal.222

(ii) Complexes with dithiocarbazate

The complexes of ruthenium(III) and rhodium(III) with thio Schiff bases

derived from S-methyl dithiocarbazate and 2-hydroxy-1-napthaldehyde and 2-

hydroxy-5-bromoacetophenone of the type [ML(HL)] (M = Ru(III), Rh(III); H2L =

methyl(2-hydroxy-1-napthylmethylene) dithiocarbazate) and methyl(2-hydroxy-5-

bromophenyl ethylidene dithiocarbazate) have been prepared and characterized223

on

the basis of various analyses.

(iii) Complexes with other sulphur donor ligands

The bimetallic compound [Ru[9]aneS3Cl]2-(µ-L)(PF6)2, [9] aneS3 = 147,

tristhiacyclonane, L = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine was formed with octahedral

geometry.224

Ruthenium(III) edta reacts with the 2-mercaptonicotinic ligand in

aqueous solution yielding a red product (530 nm) coordinated at the S atom.225

The

72

ruthenium(III) monomers [RuCl3(SRR’)3] (R = Ph, R = Me, Et, Pr, Bu, R = R’ = Me,

Et) are generally prepared226

by heating under refluxion an ethanolic solution of

RuCl3∙3H2O with an excess of RR’S.

Reactions of [RhNOX2]n (X = Cl, Br) were carried out by some aromatic

thiocarboxamides of the general form RCSNHCOR’ where R and R’ are various

substituents. The structure of the complexes was determined227

by IR and UV,

Alkylation of fac(S)-[Rh(aet)3] (aet = NH2CH2CH2S-) with use of 1,2-dibromoethane

in N,N-dimethylformamide produces fac(S)-[Rh(aet)(baete)]2+

(where baete =

(NH2Ch2Ch2SCH2)2) in which two of the three thiolato S atom in fac(S)-[Rh(aet)3] are

linked by an ethylene group. Synthesis of trimethylated complex, fac(S)-

[Rh(mtea)3]3+

have been achieved228

by treatment of an aqueous solution of fac(S)-

[Rh(aet)(mtea)2]2+

.

HSO5- oxidation of thiols coordinated to ruthenium(III) centers produces

cleanly via two discrete steps to give sulfenato and sulfinato complexes. The

preparation of several (thiolato) ruthenium(III) complexes is reported.229

The

rhodium(III) complexes [Rh(thu)6Cl3] can be obtained by heating solution of

[RhCl6]3- and thiourea.

230

Complexes of the form [Rh(S-S)2X2]Y (X = Cl, Br, Y = Cl, CIO4, 0.5 S2O8,

PF6 or BPh4), involving two different S-S bidentate [S-S = 2,5-dithiahexane(dth),

MeSCH2SMe or 1,2-diphenylthio] ethane (PhSCH2CH2SPh) have been

characterized.231

An incompletely characterized, very insoluble complex of the composition

[Rh(dth)Cl3] was also isolated. The dithioderivative of acetylacetone (sacsac) forms a

neutral diamagnetic monomer with rhodium(III). The synthesis232

of [Rh(sacsac)3]

73

requires the substitution of sulphur for oxygen in coordinated acac ligands and is

accomplished by bubbling H2S through an ethanolic HCl solution of RhCl3∙3H2O and

acetylacetone at 00C. The unsymetrically substituted dithioacacligand, o-

ethylthioacetothioacetate (o-Etsacsac), reacts with an ethanolic solution of

RhCl3∙3H2O to form [Rh(o-Etsacsac)3]. The complex has shown octahedral complex

with three bidentate ligands in a fac geometry.233

The reaction of cis-[RuCl2(TMSO)4]

with CO at various temperature and ambient pressure leads to substitution of either

one, two or three TMSO ligands with CO, depending on the choice of the reaction

conditions. Thus cis-[RuCl2(TMSO)3(CO)], cis-[RuCl2(TMSO)2(CO)2], and fac-

[RuCl2(TMSO)(CO)3] were prepared.234

Chatt et al.235

prepared complex

[RhCl3PhSR]3 by refluxing RhCl3∙3H2O with a variety of alkyl phenyl sulfides

[PhSR] (for R = me, Et, Prn, Bu

n) in MeOH.

In recent years, ruthenium(III) complexes have emerged as a new class of

effective anticancer agents against tumors that proved to be resistant to all other

chemotherapeutic drugs currently in clinical use. To extend our previous studies on

metal complexes containing sulphur donor ligands, we report here on the synthesis

and characterization, by means of several spectroscopic and analytical techniques,

some [Ru(RSDT)3] and [Ru2(RSDT)5]Cl complexes with

dithiocarbamato ligands derived from methyl/ ethyl/ tert-butyl esters of sarcosine.

Their electrochemical behaviour was also studied by cyclic voltammetry. All the

complexes were tested for their cytotoxicity on a panel of human tumor cell lines

showing highly significant antitumor activity. The chemical and biological properties

of the newly synthesized complexes, were compared with those of [Ru(DMDT)3] and

[Ru2(DMDT)5]Cl species (DMDT = N,N-dimethyldithiocarbamate) whose chemical

(not biological) characterization has been already reported in literature (XXIV).236

74

Ru RuS

S

S SS

S

S

SHHS

HS

Cl

(XXIV)

Treatment of [M(Buppy)2Cl]2 (M = Ir, Rh; BuppyH = 2-(4′-tert-

butylphenyl)pyridine) with Na(Et2NCS2), K[S2P(OMe)2], and K[N(Ph2PS)2]2 afforded

monomeric [Ir(Buppy)2(S-S)] (S

-S = Et2NCS2, S2P(OMe)2, N(PPh2S)2 and

[Rh(Buppy)2(S-S)] (S

-S=Et2NCS2, S2P(OMe)2, N(PPh2S)2, respectively. Reaction

of 1 with Na[N(PPh2Se)2] gave [Ir(Buppy)2{N(PPh2Se)2}]. The crystal structures

of 3, 4, 7, and 8 have been determined. Treatment of 1 or 2 with AgOTf (OTf =

triflate) followed by reaction with KSCN gave dinuclear [{M(Buppy)2}2(μ-SCN)2]

(M = Ir, Rh), in which the SCN− ligands bind to the two metal centers in a μ-

S,N fashion. Interaction of 1 and 2 with [Et4N]2[WQ4] gave trinuclear heterometallic

complexes [{Ir(Buppy)2}2(μ-WQ4)] (Q = S) and [{Rh(Buppy)2}2{(μ-WQ)4}] (Q = S ,

respectively. Hydrolysis of led to formation of [{Ir(Buppy)2}2{W(O)(μ-S)2(μ3-S)}]

that has been characterized by X-ray diffraction.237

The synthesis and characterization of mixed-ligand palladium(II),

ruthenium(II), rhodium(III) and iridium(III) complexes with triphenyl phosphine and

dibenzyl sulphide are reported. The complexes have been characterized by analytical,

conductance, magnetic susceptibility, IR, electronic, 1H NMR and

31P NMR spectral

75

data. Palladium(II) complex is four-corrdinated square planar and other ruthenium(II),

rhodium(III) and iridium(III) are six-coordinated octahedral.238

The overview of the inorganic and coordination chemistry of ruthenium. Since

the first edition of the encyclopedia in 1994, the field has seen a huge growth. We

have attempted to select the most useful data for the readers not familiar with this

topic and to detail the most promising systems for future developments. Key data and

recent highlights are thus presented for seven classes of compounds incorporating the

following ligands Halides: RuCl3∙xH2O is by far the most useful starting material in

ruthenium chemistry. Oxygen-donor ligands: this area is dominated by the chemistry

of oxo complexes, with many applications in catalysis. Sulphur-donor ligands:

potential applications are found in medicinal chemistry as antitumor agents and as

radiosensitizers. Nitrogen-donor ligands: they represent the most important class of

compounds in ruthenium chemistry. Supramolecular chemistry dominates, with

photo-redox processes and a wide range of applications being investigated from solar

energy conversion to bioapplications. Ammines and bipyridines (and related ligands)

are key ligands in this area. A great variety of inorganic architectures have been

designed to assemble molecular machines and to favor interactions with DNA.

Phosphorus-donor ligands: this class of compounds is at the origin of a rich

organometallic chemistry and the resulting complexes are often used as precursors in

homogeneous catalysis. The design of new ligands for the improvement of catalytic

performances is an active area of research. Group 14 ligands: this field is dominated

by the reactivity with silanes. New bonding modes, concepts and applications have

been disclosed. Hydride ligands: the most recent developments concern the chemistry

of dihydrogen complexes. The formation of dihydrogen bonds should have important

consequences on the selectivity and stereochemistry in many catalytic processes.

76

Finally, the last section is devoted to polynuclear complexes, with the new

developments in the field of nanoparticles.239

2.4. Complexes of ruthenium(III), rhodium(III) and iridium(III) with mixed

nitrogen and oxygen donor ligands

(i) Complexes with Schiff bases

The Schiff base and their complexes are well known for their important

analytical, industrial, biological and catalytic activity.240-244

The development in the

field of bioinorganic chemistry has increased the interest of Schiff base metal

complexes.245

The presence of nitrogen, oxygen and sulphur in the Schiff base makes

it an excellent ligand which on complexation with metal ions, may lead to the

formation of various rings. There are several reports indicating the synthesis of

transition metal complexes of Schiff bases which includes ruthenium(III) and

rhodium(III) metals.

Treatment of [Ru3(CO)12] with N,N’-bis(salicylaldehydo) ethylenediamine

(salenH2) in either DMF184 or toluene246

gives the dimeric yellow complex

[Ru(salen)CO]2, this compound is also formed by carbonylation247

of trans-

[Ru(salen)(PPh3O2]. Nitrosation at 60˚C in THF of [Ru(PPh3)3Cl2] affords trans-

[Ru(ONO)(salen)NO] (XXV). The reaction of [R(PPh3)3Cl2], N-(benzoyl)-N’-(5-R-

salicylidene) hydrazines (H2bhsR, R = H, OCH3, Cl, Br and NO2) and triethylamine in

1:1:2 ratio in methanol afforded mononuclear ruthenium(III) complexes having

general formula [Ru(bhsR)(PPh3)2Cl]. Where coordination occurred by bshR2 and the

chlorine atom along with two axial positions occupied by PPh3 molecules giving

distorted octahedral coordination sphere.248

Crystal structures of mononuclear

complexes are given in figure.

77

Ru

NNO

N

O

OONO

(XXV)

Oxygenation of ruthenium(III) Schiff base complexes of the composition

K[Ru(III)(saloph)Cl2] and K[Ru(III)(saloph)XCl] (saloph = bis(salicylaldehyde)-o-

phenylenediamine; X = imidazole(lm), 2-methyl-imidazole(2-Melm)) with molecular

oxygen gives the oxo derivatives of the composition, [RuV(saloph)X-(O)]

+ (X = Cl,

Im or 2-Melm).249

Synthesis and characterization of a series of ruthenium(III) Schiff base

complexes of the type [Ru(III)LXY] (XXVI) where L = Schiff base viz. bis

(naphthaldehyde)-o-phenylenediamine(naphoph), nphen, nphprop and naphdien; X =

Cl and Y = Cl imidazole or 2-Melm are reported.250

Ru

OOY

NNX

H H

W

(XXVI)

78

Interaction of Schiff bases 2-hydroxyacetophenone propylimine (happramH)

with M(CO)6 gave dicarbonyl complexes. Ru3(CO)12 and RuCl3 reacted with Schiff

base bis-(2-hydroxyacetophenone) ethylenediamine to give [Ru(CO)2(hapen)2] and

[RuCl2(hapenH2)]Cl respectively.251

Ruthenium(III) complexes with -diketones containing triphenylphosphine

and triphenylarsine with oxygen donor atoms have been prepared and reported.252

Low spin ruthenium(III) complexes [RuX(EPh3)(LL’)] (X = Cl, Br, E = P, As, LL’ =

Salen, Salph and Saldien) were synthesized by reacting [RuCl3(PPh3)3] with

tetradentate Schiff bases such as bis(salicylaldehyde)ethylenediimine (H2-Salen),

bis(salicylaldehyde) propylenediimine (H2-Salph).253

New ruthenium(III) complexes [RuX(EPh3)(LL’)] (X = Cl, Br, E = P or As,

LL’ = acactet, dbm-tet, dbm-o-ph), were synthesized by reacting [RuCl3(PPh3)3],

[RuCl3(AsPh3)3], [RuBr3(AsPh3)3] with tetradentate Schiff base. All the complexes

were found octahedral.254

Several new hexacoordinated ruthenium(III) complexes [RuX2(EPh3)(L)] (X =

Cl, Br, E = P, As, LH = o-vanillinidene-anilline and o-vanillinidene-o-toluidine, o-

vanillinidene-m-toluidine and o-vanillinidene-p-toluidine), were prepared by reacting

[RuX3(EPh3)3] or [RuBr3(EPh3)2(MeOH)] (X = Cl, Br; E = P, As) with Schiff

bases.255

Several new ruthenium(III) complexes of the formula [RuX(EPh3)(LL’)] (X =

Cl, Br, E = P or As, LL’ = anthacac, anthdibm, 2-amtpacac or 2-amtpdibm) (XXVII)

were synthesized by reacting [RuCl3(PPh3)3] and [RuCl3(AsPh3)3] with tetradentate

Schiff bases and characterized physicochemically.256

79

Ru

NN

CH2

X

ZZEPh3

R R

(XXVII)

Interaction of Schiff bases derived from the condensation of salicylaldehyde or

o-vanillin with diamines have been reported257

and characterized the complexes of

type [RuX(Eph3)(L)] (X = Cl or Br; E = P or As; L = Schiff base) (XXVIII). Schiff

base behave as dibasic tetradentate ligands and their biocidal activity have also been

observed.

Ru

OOEPh3

NNX

R R

W

(XXVIII)

The reaction of equimolar proportion of septadentate tripodal Schiff base

tris[2-salicylidene(amino)ethyl]amine H3L and RuCl3∙3H2O in MeOH resulted258

in

[RuL]CH2Cl2H2O. Schiff bases obtained by direct condensation of anthracitic acid

benzaldehyde, acetophenone, vanillin cinnamaldehyde or m-hydroxyacetophenone

and their ruthenium(III) complexes have been synthesized and are repoted with their

physicochemical characterization.259

80

A series of several octahedral rhodium(III) salen type complexes (XXIX)

where the salen ligand is unsymetrically bound to be the rhodium(III) dichloride

centre was reported. This mode of bonding left one intact phenol group coordinating

to the rhodium centre and has never before observed in salen-metal chemistry.260

Ru

OOCl

NNCl

Z

R'

t-Bu

R'

t-Bu

(XXIX)

The rhodium(III) complexes and others with 4-vanillideneamino-3-methyl-5-

mercapto, 1,2,4-triazole were synthesized261

and octahedral structures are proposed.

The compounds of ruthenium(III) and rhodium(III) with 4-Salicylideneamono-3-

mercapto,1,2,4-triazine(4-H)-5-one(SAMT) were synthesized and octahedral structure

was proposed.262

When a mixture of RhCl3∙3H2O with Zn dust is added to a hot

pyridine solution containing N,N’-ethylenebis(salicylideneiminate) (the Schiff base

salen), yellow crystals of [Rh(salen)py(Cl)] (XXX) formed.263

The reaction of

[Rh(salen)Cl(py)] with Na(Hg) or BH4 in the presence of organic halides lead to

[Rh(salen)R(py)] (R = Me, Et, Prn, Bu

n, MeCO, aniline).

Ru

OO

NN CC

Py

Py

C C

(XXX)

81

The [Rhpy4Cl2]+ ion reacts readily with a variety of Schiff bases in boiling

pyridine solution (in the presence of Zn dust and PF6-), to generate

264 a family of

complexes of the form [Rh(SB)py2]PF6 (XXXI).

O-

C

H

N

-O

C

H

NB

(XXXI)

(B = 1,2-phenylene; 4-methyl-1,2-phenylene; ethylene; 1,3-propylene; 1,4-butylene)

Binuclear complexes containing a binucleating Schiff base ligand L and PPh3

or Ph3As, [RuX2(Eph3)2]2L (X = Cl or Br; E = P or As) were prepared265

by reacting

(RuCl3(PPh3)3], (RuCl3(AsPh3)3], [RuBr3(AsPh3) and [RuBr3(PPh3)2(MeOH] with

Schiff bases266

in 2:1 molar ratio.

The macrocyclic compartmental Schiff base ruthenium(III) complexes have

been synthesized. A variety of complexes have been obtained by different procedures

and also depending on the choice of lateral diamine fragments with ruthenium ions.

The compounds were characterized by elemental analyses, conductometric and

magnetochemical behaviour, as well as by IR, ESR, TG, electrochemical and

electronic spectra. The antimicrobial activities of the ligands and the complexes have

also been tested (XXXII, XXXIII).267

82

Ru

O

ON

N

O

O

X

CH3

CH3

(XXXII)

Ru

Cl

ClN

N

O

O

X

CH3

CH3

Ru Cl

HN

HN Ph

Ph

(XXXIII)

83

(ii) Complexes with amino acids

Treatment of [RuCl2(diene)]n (diene = nbd, 1,5-cod) with aqueous solution of

glycine (GlyH) at reflux yields two isomers of the [Ru(Gly-O)2(diene0]H2O which

were successfully separated.268

The nitrosyl complexes K[Ru(Gly-O)(OH)3NO] and

K[Ru(Ala)(OH)3NO] arise from reaction of aqueous [RuCl3(OH2)2NO] with the

glycine269

and L-α-alanine270

respectively, followed by the anion exchange with

2MKCl; [RuCl2(Ala)4] has also been clamied.271

The brief reports272

have been published on the reaction of the RuCl3∙3H2O

with tris(hydroxymethyl)aminoethane(thamH) with give [RuCl(tham)]2Cl2 and

[RuCl2(DMSO)4] and N-glycylglycine (Gly-Gly) with forms [Ru(Gly-Gly)(DMSO)3].

Reactions of RuCl3∙3H2O with equimolar amounts of glycine gives the

polymeric [RuIII

(gly)(N-O)]∙H2O. Synthesis and characterization of several chiral

ruthenium(III) Schiff base complexes of the type K[RuLCl2(H2O)] (H2L = Schiff base

derived from L-amino with salicylaldehyde) (XXXIV) are reported by Khan et al.273

Ru Cl

ClO

N

OH2

O

K+

-

(XXXIV)

84

The Complexes of ruthenium(III) derived from ligands of amino acids with

isatin in ethanolic medium were prepared and they have shown octahedral

geometry.274

Amino acid complexes of rhodium(III) are relatively rare,275

but some

[Rh(en)2(AB]n+

complexes (AB = glycine, alanine, (-)-Leucine, (-)-methionine, (-)-

Valine, (-)-phenylalanine, (-)-tyrosine) have been prepared276

by reacting equimolar

mixture of Cis or trans-[Rh(en)2Cl2]+, OH and the approapriate amino acid in an

ethanol/ water (1-3) solution. In the absence of the reducing ethanol, no reaction is

observed. The preparation of the gly and ala complexes using BH4 catalysis has been

reported.277

Reaction of RhCl3·3H2O with sodium bicarbonate causes precipitation of

Rh2O3, which forms [Rh(D-ala)3] if heated immediately with D-alanine. Reaction of

Li salf of DL-methionine (Li+MeSCH2CH2CH(NH2)COO

-) with anhydrous RhCl3 in

refluxing ethanol leads to the precipitation of [Rh(DL-methionine)3], in which the

methionine act as an anionic bidentate bonded through oxygen and nitrogen atom.278

The solid state reaction of RhCl3 with glycine is reported279

to lead the [Rh(gly)3].

The synthesis and structural characterization of ruthenium(III) complexes of

formula[Ru(L)2]Cl, LH = Schiff bases derived from isatin and series of various amino

acid [viz. ɑ-alanine (lalaH), aspartic acid (IaspH), glutamic acid (IgluH), ɑ-glycine

(IglyH), ᵦ- phenyl-ɑ-alanine (IphalaH), serine (IserH), threonine (IthreH) and valine

(IvalH)]. On the basis of elemental analyses, molar conductance, magnetic

susceptibility, electronic and infrared studies it can be concluded that the LH act as a

monobasic tridentate O, N, O donor towards the studied metal ions. The complexes

are monomeric and their geometry is octahedral. The ligands and their metal

85

complexes have been screened in vitro for antifungal activities. The results indicate

that in all complexes antifungal activitiy of ligand increases on complexation due to

chelation (XXXV).280

NH

N

O

M

CH C

R O

OHN

N

O

C HC

RO

O

X = Cl; OAc

(XXXV)

(iii) Complexes with oximes

Reaction of RuCl3∙3H2O with a α-benziloxime [PhC(=O)(=NOH)Ph](HB)

gives products281

formulated on the basis of IR, EPR data as trans-[Ru(III)X2(HB)B]

(XXXVI).

CH

CHN

Ru

OR1

R

CH

CHN

OR1

R

O OH

(XXXVI)

86

Similar reactions282

occur with an arylazooximex [Rc(=NOH)N=NAr] to give

[RuX2(HL)L]. An unusual hydroxyiminoketone complex is obtained by reaction of

Ru(OH)3NO with acacHat pH 6.5 either cis-[Ru(acac)2(Cl)NO] or [Ru(acac)2NO]4 is

formed. Sharma et. al.283

reported that reaction of RuCl3 and RhCl3 with neural

chalcone oximes give M(HL)3Cl3 and ML3 (M = Ru(III), Rh(III), HL = chalcone

oxime). The octahedral geometry was proposed for these complexes. Reaction of

[Ru(VR2)3] anion with Na[NO2] in HClO4 gives [Ru(VR2)3NHO], whereas treatment

with Na[NO2] in hydrohalic media yields [RuX(VR2)2NO] (where R = H, Me, X = Cl,

Br).284

The synthesis, characterization and electron transfer behavior of RuCl2(HL)L

and RuBr2(HL)L (HL = α-benzil monoxime) are described.285

Dichloro 4,4-(1,2-

ethanediylimino)bis(u-methyl-2-pentanedioxime) rhodium(III) crystallizes with

octahedral configuration (XXXVII) with cis-amine nitrogens and cis-oxime

nitrogen.286

Rh

N

NCl

N

N

Cl

C

CH3

CH3

CH3

O O

H

C

H3C

H3C

CH2

(XXXVII)

The reaction of RhCl3∙3H2O with Hdamo and PPh3 (Hdamo = diacetyl

monoxime = C4H6NO), both in absence and presence of the HClO4 afforded287

Rh(damo)(PPh3)2ClO4].

87

Synthesis of bis azooximates occurred by reaction of azooximes

RC(NOH)NNPh (R = Me, HL1, R = C6H4Me-p, HL

3) with the RhCl3∙3H2O afforded

red trans–cis[tcc-RhCl2L(HL)] which was converted into green [NEt3H][tcc-RhCl2L2]

upon treatment with Et3N. The crystal structure of tcc[RhCl2L2(HL2)] and

NEt3H][tcc-RhCl2L2

2] were determined and reported.288

Reaction of [RhCl3(MeCN)3] with 2-propanone oxime Me2C=NOH or

alternatively interaction of the [RhCl3(Me2C=NOH)3] and MeCN gave to

rhodium(III) products289

that contain newly formed chelated iminoacyl ligands i.e.

[RhCl3(NH=C(Me)ON=CMe2)].

Biacetyl monoxime phenoxyacetyl hydraxone was used in synthesis290

of

[RhCl3(MeCN)3] with cyclopentanone oxime (C4H8)C=NOH resulted in the

formation of two rhodium(III) products291

that contain newly formed

chelatediminoacyl ligands i.e. [RhCl3-NH=C(Me)ON=C(C4H8){HON=C(C4H8)} and

[RHCl2{NH=C(Me)ON=C(C4H8)}2]Cl∙5H2O. X-ray single crystal analyses were

performed on complexes [RhCl3{NH=C(Me)ON=C(C4H8)}{HON=C(C4H8)}] as well

as on complex [RhCl2{NH=C(Me)ON=C(C4H8)}]+ .

The complex of type ML3 (M = Rh, lr; HL = 1,2-naphthaquinone-1-oxime

(1nqOH), 1,2-naphthaquinone-2-oxime) have been prepared292

by the interaction of

the quinine oxime with hydrated RhCl3 or lrCl3. Rhodium(III) chloride reacted with 2-

(hydroxyamino)-2-methyl-1-phenyl-1 propanone oxime in aqueous alcoholic solution

to give compounds293

with octahedral geometry (XXXVIII).

88

CH

CHN

Ru

NCH

CHN

NMe2

Ph

O O

O

Ph

Me2

O

H+

-

Cl

Cl

(XXXVIII)

A group of ruthenium(III) complexes of type [RuX2(HL)(L)] (HL = R’

C(=O)C(=NOH)R; (X = Cl or Br) (XXXIX) have been prepared.294

Where the RuX2

group is trans as given in figure.

Rh

O

NX

O

N

X

O OH

(XXXIX)

Coordination of ruthenium trichloride with hydrazones derived from

diacetylmonoxime and substituted benzoyl hydrazides [viz. diacetylmonoxime

benzoylhydrazone (DMBH), diacetylmonoxime isonicotinoylhydrazone (DMINH),

diacetylmonoxime nicotinoylhydrazones (DMNH), diacetylmonoxim 2-

chlorobenzoylhydrazones (DMOCH), diacetylmonoxime 4-chlorobenzoylhydrazone

(DMPCH), diacetylmonoxime 4-methoxybenzoylhydrazones (DMPMH),

diacetylmonoxime 4-nitrobenzoylhydrazones (DMPNH) and diacetylmonoxime 4-

methylbenzoylhydrazone (DMPTH)] has been studied and dinuclear complexes of the

type [Ru(L)Cl(H2O)]2Cl2 have been isolated. Octahedral complexes are characterized

89

by elemental analyses, molar conductance, magnetic susceptibility, electronic,

infrared, 1H NMR, mass and thermal studies. The infrared spectra show that the

hydrazones behave as bidentate ligands either in the amide or imido form. The ligands

and their metal complexes have been screened in vitro for antibacterial and antifungal

activities. The results indicate that in the complexes the biocidal activity of the ligand

increases on complexation (XXXX).295,296

Rh

O

NCl

O

N

Cl

C

HN

CH3H3C

O

RN

Ru

OH2 N

H3CCH3

NH

C

ROCl

Cl2

(XXXX)

(iv) Complexes with other nitrogen and oxygen donor ligands

The dianion of diplicolinic acid (dipic) acts as a tridentate, forming

Na[Rh(DipiC)2] and a series of complexes of the type [Rh(dipic)(N-O)]n∙H2O (N-O =

N and O donating bidentate) (XXXXI) formed.297

The bis complexes are diamagnetic

monomers with octahedral structure.

90

N

C

C

O

O

O

O

Ru

2

-

(XXXXI)

New hexacoordinated ruthenium(III) complexes of the type

[Ru(dipic)(EPh3)2X] (XXXXII) have been synthesized298

by reacting 2,6-

pyridinedicarboxylic acid (dipicolinic acid, H2dipic) with the appropriate starting

complexes [RuX3(EPh3)3] (where X = Cl, Br; E = P, As). The ligand behaves as

tridentate dibasic chelate. Dipicolinic acid which was expected to form a bridge

between two metal centers formed only mononuclear complexes irrespective of the

metal to ligand ratio which was confirmed by X-ray analysis.

N

C

C

O

O

O

O

Ru

Ph3E

Ph3E

X

(XXXXII)

91

A series of new mixed ligand hexacoordinated ruthenium(III) Schiff base

complexes of the type [RuX2(EPh3)2(LL’)] where X = Cl, E = P; X = Cl or Br; E = As

and LL’ = anion of the Schiff base derived from condensation of 2-hydroxy-1-

naphthaldehyde with aniline, 4-chloroaniline, 2-methylaniline and 4-methoxyaniline)

(XXXXIII) are reported.299

CH

N

Ru

Ph3E

Ph3E

X

R

O

(XXXXIII)

Ruthenium(III) edta complexes can be attached to a graphite electrode surface

via the uncoordination carboxylate function and some redox couples [Ru(edta)L]-/2-

complexes reported.300

The low spin ruthenium(III) triazine-1-oxide complexes (R =

Et, X = Me, H, Cl, NO2, CO2Et) have been prepared and assigned301

a meridional

RuN3O3 coordination sphere. Complexes [Ru(Met)2(L)2]Cl (HMet = methionine, L =

isoniazide, α-aminopyridine, 1,2-diMe-5-nitroimidazole), [Ru(Hip)2(L)2]Cl (Hip =

hippuric acid, L = isoniazide) were prepared and characterized.302

Octahedral Ru(II)/

(III) compound [Ru(Y)(CO)(BAX)(PPh3)2] and [RuCl2(BAX)(PPh3)2] (Y = H or Cl,

BAX = Benzaldehyde acetyl hydrazone anion, X = H, Me, OMe, OH, Cl or NO2)

were prepared.303

Several new ruthenium(III) complex [RuX(LL’)(EPPh3)3] (X = Cl, Br; LL’ =

Schiff bases namely, bis(aminophenol) (apg), bis(aminophenol)benzyl (apb) or

(amino thiol) glyoxal (atg); E = P or As) were prepared.304

92

Reaction of phenolate ligands viz. N-(2-pydroxyphenyl) salicylaldimine

(H2L1), 2,2’-dihydroxyazobenzene (H2L2), N-2(xarboxyphenyl)salicylaldimine (H2L3)

and 2-carbozxy-2’-hydroxy-5’-methyl azobenzene (H2L4) where H stands for acidic

protons has been carried out305

with [Ru(trpy)Cl3] (trpy = 2,2’,2”-terpyridine).

Rhodium(III) and ruthenium(III) complexes of propiophenone and

butyrophenone semicarbazones have been synthesized306

and complexes have

compositions M(ligand)2Cl2 and M(ligand)3Cl3 (M = Rh and Ru).

New tetradentate (O2N2) Schiff base Ru(II)/ (III) complexes were prepared

and their properties were studied.307

The reaction of HRL (R = Me, Et) with

K2[RuCl5(H2O) has afforded Ru(III)(RL2)(PPh3)Cl. The two phenolic oxygen and

azomethine nitrogen atoms involved in coordination.308

The reaction of K2RuCl5∙H2O with (C5H4N)P(O)(OEt)2(L) yields the anionic

complex K[RuCl2(OP(O)(OEt)(C5H4N]2, One ethyl group of L has been eliminated in

an Arbuzov–Type reaction. Fluxional compounds MCl3L2 with one bidentate and one

monodentate ligands were prepared by reaction of L with MCl3∙3H2O (M = Ru, Rh)

and are reported.309

A series of several new reuthenium(III) and rhodium(III) complexes of 2,6-

diacetylpyridine bis(benzoylthydrazone) were prepared310

and characterized by

spectroscopic and magnetic studies. Singh et al. reported311

that semicarbazones

usually act as a chelating agent by binding through nitrogen and oxygen atom to

rhodium(III) metal and result in octahedral geometry. Same complex of rhodium(III)

with 4-amino antipyrine semicarbazone was prepared and characterized

physiochemically.

93

Rhodium(III) complexes with salicylaldehyde hydrazones were synthesized312

and studied by analytical methods. Carboxylic acid salicylidene hydrazones are

coordinated by rhodium(III) as tridentate through oxygen and nitrogen of azomethine

group. Carbxylic acid salicylidenehydrazones are coordinated by rhodium(III) in a

tridentate cyclic manner by oxygen atom of carbonyl and hydroxyl group and

azomethine atom of nitrogen.313

Dwyer and garvan also prepared and reported314

the ruthenium(III) complexes

of 1-propylenediaminetetraacetic acid (pdta) and suggested it as a five coordinate

chelate forming out [Rh(pdta)(H2O)]. Reaction of picolinic acid with rhodium

trichloride affirds tris-picolinate complexes of type [M(pic)3]. In both complexes, the

picolinate anion coordinate to the metal center as bidentate forming five membered

chelate rings.315

Ligands coordinates to metal as two isomeric forms, viz facial

(XXXXIV) and meridional (XXXXV). The X-ray crystal structure of the complex

[M(pic)3] confirmed the exact geometry.

M

N

O

N

O

N

O

M

N

O

O

O

N

N

(XXXXIV) (XXXXV)

Nitritotriacetate (NTA), N-methylimino diacetate (MIDA) and iminodiacetate

(IDA) (XXXXVI) form a series of 1:1 and 1:2 (metal:ligand) complexes with

rhodium(III).316

94

HO

C

CH2

NR

HO

O

CH2

O

(XXXXVI)

M. E. Sheridan et al. have recently presented317

an interesting series of reports

on the rhodium(III) complexes formed with the optically active tetradentate ligand

ethylenediamine- N,N’-di-S-propionate, (S-S-eddp).

A series of octahedral ruthenium(III), rhodium(III) and iridium(III) complexes

have been prepared with tetradentate Schiff bases derived by condensing isatin with

1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,2-diaminobenzene and

1,3-diaminobenzene. The obtained complexes were characterized on the basis of their

elemental analyses, magnetic moment, conductance, IR, electronic, 1H NMR and

FAB mass spectra, as well as thermal analyses. The ruthenium(III) complexes are low

spin paramagnetic, while rhodium(III) and iridium(III) behave as diamagnetic

complexes. The IR spectral data revealed that all the Schiff bases behave as

tetradentate and are coordinated to ruthenium(III), rhodium(III) and iridium(III) via

nitrogen and oxygen. Antifungal studies of the ligands as well as their complexes

were carried out by the agar plate method (XXXXVII).318

95

NH

N

O

M

NH

N

O

Cl

Cl

R

Cl

M = Ru(III), Rh(III), Ir(III)

R = (CH2)2, (CH2)3, (CH2)4, 2-C6H4, 3-C6H4

(XXXXVII)

Nine novel acyclic hydrazone ligands, FINH=N-(furylidene)-N′-

isonicotinoylhydrazine, FNH=N-(furylidene)-N′-nicotinoylhydrazine, PINH=N-

(pyrienylidene)-N′-isonicotinoylhydrazine, PNH=N-(pyrienylidene)-N′-

nicotinoylhydrazine, TINH=N-(thienylidene)-N′-isonicotinoylhydrazine, TNH=N-

(thienylidene)-N′-nicotinoylhydrazine, FSH=N-(furylidene)-N′-salicyloylhydrazine,

PSH=N-(pyrienylidene)-N′-salicyloylhydrazine and TSH=N-(thienylidene)-N′-

salicyloylhydrazine, have been synthesized. Their corresponding mononuclear and

binuclear ruthenium(III) complexes have been prepared by the reaction of the ligand

with RuCl3·3H2O in 1:2 and 2:2 molar ratio and are characterized by elemental

analyses, thermogravimetric analyses (TGA and DTG), IR, electronic, magnetic

susceptibility and electrical conductance measurements. Electronic spectra and

magnetic susceptibility measurements of the solid complexes (both mono and

binuclear) indicate an octahedral geometry around ruthenium(III). Particular emphasis

is given to the binuclear complexes in which FSH, PSH and TSH behave as tridentate

96

ligands and chloride bridges the ruthenium(III) ions. Conductance measurements

show the mononuclear complexes are electrolytic and binuclear complexes are of

non-electrolytic. The fungicidal activities of the ligands and metal complexes

against Fusarium oxysporium and Aspergillus niger are described (XXXXVIII),

(XXXXIX) and (L).319

C

HNN

Ru

O

CH

N

R

C

NHN

O

HC

N

R

Cl

Cl

Cl

(XXXXVIII)

C

HNN

Ru

O

CH

N

R

C

NHN

O

HC

N

R

Cl

Cl

Cl

(XXXXIX)

97

CH

HNN

Ru

O

CH

R

O

CH

NHN

Ru

O

HC

R

O

Cl

Cl

(L)

A series of several new ruthenium(III), rhodium(III) and iridium(III)

complexes with hydrazones of general formula [M(LH)3]Cl3 were synthesized in

order to meet requirements essential for biological properties. Hydrazones were

formed by isatin hydrazide and various aldehydes namely anisaldehyde,

benzaldehyde, o-chlorobenzaldehyde, p-chlorobenzaldehyde and p-

fluorobenzaldehyde. Physicochemical characterization of compounds has been carried

out by elemental analyses, spectroscopic (IR, electronic, 1H NMR),

thermogravimetric and magnetic studies. These complexes show higher conductance

values, supporting their electrolytic nature. All the studies revealed octahedral nature

of the complexes with nitrogen and oxygen of azomethine and carbonyl group as

binding sites and exhibited monomeric nature of the complexes. Rhodium(III) and

iridium(III) complexes were found diamagnetic and show intense absorptions while

ruthenium(III) complexes show paramagnetic behavior (LI).320

98

N

H

N

O

N CH

R

M

3+

3

R = 4-OCH3, H, 2-Cl, 4-Cl, 4-F

M = Ru(III), Rh(III), Ir(III)

(LI)

Amide group containing ligands are biologically potent and there are several

examples of in vivo interactions of transition metal ions with these ligands1, 2. The

metal complexes of amide group ligands serve as models for metalopeptide

interactions and metalloenzymes in which the properties of peptides are modified by

the fact that the metal ions are attached to them. An amide group offers two potential

binding atoms, the oxygen and nitrogen, for complexation with metal ions.

Aminopterin, D-penicilamine, phenylalanine mustard and 6-mercaptopurine, all

possessed an amide group, show an increased anticancer activity when administered

as metal complexes. A series of nickel, palladium and platinum complexes and some

of the rhodium and iridium complexes have been reported in this regard. In the

present investigation, the synthesis and structural characterization of the complexes of

ruthenium(III) with 3-phenyl-4-benzamidoetheneyl-b-carboxy-5-isoxazolone

(PBECI), b-(3-methyl-4 isoxazolylamido-5-styryl)benzoic acid (4-MIABA), b-(3-

99

methyl-4-isoxazolylamido-5-styryl)acrylic acid (4-MIAAA), b-(3-methyl-4-

isoxazolyl-amido-5-styryl)propionic acid (4-MIAPA), b-(5- methyl-3-

isoxazolylamido)benzoic acid (3-MIABA), b-(5-methyl-3-isoxazolylamido) acrylic

acid (3-MIAAA) and b-(5-methyl-3-isoxazolylamido)-propionic acid (3-MIAPA)

were reported.321

The trivalent ruthenium, rhodium and iridium complexes of dipicolinic acid

and its mixed ligand complexes with several nitrogen, oxygen donor molecules, of

types: Na[M(dipic)2]·2H2O and [M(dipic)(N-O)]·nH2O (where M = Ru(III), Rh(III)

or Ir(III); dipicH2 = dipicolinic acid; NOH represents different nitrogen, oxygen donor

molecules, viz., picolinic acid, nicotinic acid, isonicotinic acid, glycine,

aminophenol, o- or p-aminobenzoic acid) have been synthesized and characterised on

the basis of elemental analyses, electrical conductance, magnetic susceptibility

measurements and spectral (electronic and infrared) data. The parent dipicolinic acid

complexes are found to have a six-coordinate pseudooctahedral structure, whereas for

mixed ligand complexes, a polymeric six-coordinate structure has been assigned.

Various ligand field and nephelauxetic parameters have also been evaluated.322

2.5. Complexes of ruthenium(III), rhodium(III) and iridium(III) with mixed

nitrogen and sulphur donor ligands

(i) Complexes with thiosemicarbazides and thiosemicarbazones

Many thiosemicarbazone complexes with ruthenium(III) have been reported.

Treatment of RuCl3∙3H2O with 4-benzylamidothiosemicarbazide(btsc) and α-

pyridylthiosemicarbazide(apt) gives the ruthenium(III) cations [RuCl2(btsc)2]Cl∙2H2O

and [RuCl2(apt)2]Cl repectively. With 1-benzilidene-4-α-pyridylthiosemicarbazone

(bpt). [RuCl3(bpt)] is produced.323,324

100

The platinum metal chelates of benzoin thiosemicarbazones obtained with

ruthenium(III) and rhodium(III) were reported from their corresponding halide salts.

The complexes were reported325

as octahedral. Offiong et al.326

synthesized and

characterized [2-acetylpyridine-2-methylthiosemicarbazone], 2-acetylpyridine-

4(methylthiosemicarbazone), 2-acetylpyridine-(4-phenylthiosemicarbozone) and their

ruthenium(III) and rhodium(III) complexes, which were also studied by their

antibacterial, antifungal and amoebicidal activity in vitro. Synthesis of o-vanillin-(4-

methylthiosemicarbazone), o-vanillin-(4-phenylthiosemicarbazone) and some of their

metal complexes of platinum group occurred and complexes were characterized327

physicochemically. The ruthenium(III) chelates were found as most suitable inhibitors

against various biological activities.

[M(HL)2]Cl3 (M = Ru(III) and Rh(III) were prepared328

(were HL = 2-

acetylpyridine-(2-methylthiosemicarbazone), 2-acetylpyridine-(4-

methylthiosemicarbazone) or 2-acetylpyridine-(4-phenylthiosemicarbazone)).

Ruthenium(III) and rhodium(III) complexes were found pseudooctahedral with

tridentate nature of ligand. Heptacoordinate compounds containing the pentadentate

SNNNS chelating ligands 2,6-Diacetylpyridine bis(4-p-tolyl) thiosemicarbazone

(L1H2) were prepared.329

Several hexacoordinated low spin d5 ruthenium(III)

complexes [RuX2(TSC)(EPh3)2] (X = Cl, Br, HTSC = benzaldehyde

thiosemicarbazone, cinnamaldehyde thiosemicarbazone, thiophene-2-carboxaldehyde

thiosemicarbazone and 2-furanaldehyde thiosemicarbazone, E = P or As) were

synthesized.330

Ruthenium(III) complexes, [RuX3(PPh3)2(L)] (X = Cl, Br, E = P, As, L =

tridentate Schiff base dianion) (LII), have been synthesized331

by reacting

[RuCl3(PPh3)3] with thiosemicarbazones of methyl and ethyl derivatives.

101

HC

C

H3C

N

R

O

Ru

EPh3

EPh3

S

X

CH

NHR'

(LII)

4-R-C6H4CH:NNHC(S)NH2 (HL-R; R = H, OMe, NO2) react with

[Ru(PPh3)3Cl3] in refluxing ethanol in presence of NEt3 to afford the [M(PPh3)2(L-

R)2] complex in which thiosemicarbazone is coordinated as a bidentate N, S donor.332

Solid metal complexes of 2-hydroxy-1-naphthaldehyde thiosemicarbazone with

ruthenium(III) were prepared and characterized physicochemically.333

The complexes

of 2-hydroxy-1-naphthaldehyde thiosemicarbazone with transition metal

ruthenium(III) were also prepared.334

Synthesis of ruthenium(III) and rhodium(II) complexes with 4[N-furan-2’-

(carboxalidene)aminoantipyrine] thiosemicarbazones occurred along with their

spectral characterization.335

Salicylaldehyde allyl thiosemicarbazone (H2L) was

prepared by the condensation of salicylaldehyde with allylthiosemicarbazide H2L

reacted with RhCl3 to give [Rh(HL)2]Cl, Na[RhL2] and [Rh(HL)]L. The complexes

have shown octahedral geometry.336

Cyclohexanone thiosemicarbazide reacts with RhCl3∙3H2O in refluxing

ethanol to form the 3:1 electrolyte [Rh(HL)3]Cl3 in which the neutral semicarbazide is

a sulfur and nitrogen bonded bidentate. The conjugate base also forms the

nonelectrolyte [Rh(L)3] in which the anionic thiosemicarbazide is again and N- and S

102

bonded bidentate. These complexes were characterized by conductivity measurements

and magnetic susceptibility.337

Thiosemicarbazidodiacetic acid (H2L) reacts with RhCl3∙3H2O in ethanol in

the presene of Lewis bases forming338

[Rh(L)(B)Cl]nH2O (B = OH-, Py, α-picoline,

PPh3, aniline) in the presence of bipy or phen(NN), the product is formulated as

[Rh(L)(NN)]Cl (LIII).

C

S

HN N

C

CH2

COOH

H2N

HOO

(LIII)

Some complexes of 4-methoxybenzaldenhyde-4-phenyl-3-thiosemicarbazone

(MBPT) with ruthenium(III) and rhodium(III) metal ions have been synthesized339

and characterized. All complexes are hydrated crystalline powders decomposed by

mineral acids.

Ruthenium(III) and rhodium(III) complexes of 2-furfuralthiosemicarbazone as

ligands have been synthesized.340

These complexes have the composition [M(ligand-

H)2X2]X (M = Ru(III), Rh(III); X = Cl and Br). The deprotonated ligands forms the

complexes of the formula [M(ligand)3].

The synthetic, spectroscopic and biological studies of sixteen ring-substituted

4-phenylthiosemicarbazones and 4-nitrophenyl-thiosemicarbazones of anisaldehyde,

4-chlorobenzaldehyde, 4-fluorobenzaldehyde and vanillin with ruthenium(III) and

103

rhodium(III) chlorides are reported here. Their structures were determined on the

basis of the elemental analyses, spectroscopic data (IR, electronic, 1H and

13C NMR)

along with magnetic susceptibility measurements, molar conductivity and

thermogravimetric analyses. Electrical conductance measurement revealed a 1:3

electrolytic nature of the complexes. The resulting colored products are monomeric in

nature. On the basis of the above studies, three ligands were suggested to be

coordinated to each metal atom by thione sulphur and azomethine nitrogen to form

low-spin octahedral complexes with ruthenium(III) while forming diamagnetic

complexes with rhodium(III). Both ligands and their complexes have been screened

for their bactericidal activities and the results indicate that they exhibit a significant

activity (LIV).341

R N

H

C

N

S

H

N

CH

R'

R"

M

N

S

S

N

Cl3

M = Ru(III), Rh(III)

(LIV)

104

Some extremely novel and hitherto unknown complexes of isatin

thiosemicarbazone and substituted thiosemicarbazones with ruthenium(III) have been

synthesized and characterized by elemental analysis by spectral (FT-IR, 1H NMR,

UV-Vis, mass), magnetic, thermal and conductance studies. All complexes are

crystalline powders decomposed by mineral acids. The spectral and other data

indicate that all the ruthenium(III) complexes are tetrahedral. The ligand, its Schiff’s

bases and and metal chelates would be screened in-vitro for anticancer activity against

some cancer cell lines.342

(ii) Complexes with thianthrene and phenoxanthin

RhCl3∙3H2O with thianthrene (Q) and phenoxanthin

(L) have been studied. The complexes RhQCl3 were isolated and characterized343

by

electronic, IR and NMR spectra.

(iii) Complexes with thiadiazole and triazole

Complexes of ruthenium(III) and rhodium(III) with 1, 3, 4-thiadiazole-2, 5-

dithiol (Htdt) have been reported by Gajendragad et al.344

and the complexes of type

Ru(Htdt)2Cl∙2H2O and Rh(Htdt)2Cl have been isolated.

Ruthenium(II)/ (III) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-

7(4H)-one (HmtpO) of the formula cis-[RuCl2(dmso)3(HmtpO)] (1) and trans-

[RuCl4(dmso)(H2mtpO)]·4H2O (2) have been synthesized and characterized using

different spectroscopic techniques (IR, 1H–

15N HMBC,

1H–

13C HSQC,

1H–

13C

HMBC and EPR). Spectroscopic studies reveal a monodentate coordination of the

heterocycle ligand (HmtpO) via N3 to the ruthenium(II) and ruthenium(III) ions. In

addition, the X-ray crystal structure was determined for complex (2). The compound

105

crystallized in the triclinic group Formula Not Shown . The asymmetric unit of the

structure consists of two complex molecules (2a and 2b) and 8 water molecules. The

equatorial positions are occupied by four chloride ions, while the N3 bonded,

protonated H2mtpO+ and S-bonded dmso ligands are located in axial

positions. Complex (1) has been screened for in vitro cytotoxicity against two human

cells: non-small cell lung carcinoma (A549) and breast cancer (T47D). The

ruthenium(II) complex was found to be less active than cisplatinum.345

(iv) Complexes with heterocyclic thiones

Some benzoxazole-2-thione(bot) complexes ruthenium(III) were prepared and

characterized.346

A series of bebzoxazole-2-thione(bot) complexes of general formula

[M(bot)3X3] (M = Rh(III); X = Cl, Br, I) were also prepared.347

The complexes of type [RhLCl2(H2O)] (L = 5-methylthioethyldantion) have

been prepared348

form RhCl3 and Lin Solution of Ph~3. Complexes of 2-mercapto-

thiazoline (L) with ruthenium(III) of types [Rh(III)(L)4Cl2]+ and [Rh(III)(L)4Cl2]

-3

have been prepared and characterized349

by IR, far IR and NMR. Coordination

behaviour of one important class of heterocyclic thione donors viz. thiohydantoins

towards ruthenium(III) and rhodium(III) was studied with composition [M(L)3] (LV)

and characterized.350

106

MN

S

C

NR

C O

CH2

N

S C

N RN

CH2

OSCN

R

C

OCH2

(LV)

Ruthenium(III) and rhodium(III) complexes of 3-(o-hydroxyphenyl)-4-amino-

1,2,4-triazoline-5-thione (HL) and 3-(o-hydroxyphenyl)-4-(o-

hydroxybenzylideneamino)-1,2,-triazoline-5-thione (H2L’) of type ML3 and ML’

(HL’) (M = Ru, Rh) have been prepared.351

Rhodium(III) complexes with

quinazoline-2-thione-4-one (HQ) of the type [RhQ2Cl(H2O)] has been prepared352

and

characterized by IR.

Complexes of dithiouracil (LVI) with rhodium(III) have been prepared.353

The

structures of the complexes have been ascertained by using infrared and electron

spectroscopy for chemical analysis (ESCA) and the result compared to those form

other pyrimidine complexes.

NH

HN S

S

(LVI)

107

Complexes of ruthenium(III), platinum(IV), rhodium(III), palladium(II) and

platinum(II) with 3-(o-hydroxyphenyl)-1,2,4-triasoline-5-thione (pttH) and 3-(o-

hydroxyphenyl)-4-(o-hydroxy-benzylidine)-1,2,4-triasoline-5-thione (HO-bttH) have

been synthesised and characterised on the basis of elemental analyses and infrared and

electronic spectra and magnetic susceptibility measurements. The palladium(II) and

platinum(II) Complex are square planar, whereas ruthenium(III), platinum(IV) and

rhodium(III) Complexes posses pseudooctahedral stereo chemistry. Various ligand

field and nephelauxetic parameters have been evaluated wherever possible.354

A family of novel platinum group metal complexes containing bidentate

chelating 1-pyrimidyl-3-methylimidazolyl bromide (HL1·Br) and 1-pyrimidyl-3-

methylimidazolyl-2-thione (L2) ligands has been synthesized. The synthetic protocol

for the formation of these complexes differs from one ligand to the other. Treatment

of ligand (HL1·Br) with the metal precursors led to the formation of complexes via in

situ carbene transfer reactions. The silver–NHC complex (1) was formed by the

reaction of HL1·Br with silver oxide under light-free conditions. Subsequent addition

of appropriate metal precursors to the silver–NHC complex yielded [(η6-

arene)Ru(L1)Cl]PF6 complexes {arene = C6H6 (2), p-iPrC6H4Me (3), C6Me6 (4)} on

stirring at room temperature, whereas the complexes

[CpRu(L1)(PPh3)]PF6 {Cp = C5H5 (5), C9H7 (6)} were obtained under reflux

conditions. In the case of ligand L2, stirring of equimolar quantities of metal

precursors and the ligand at room temperature yielded [(η6-

arene)Ru(L2)Cl]PF6 {arene = C6H6 (7), p-iPrC6H4Me (8), C6Me6 (9)}, and

[Cp∗M(L2)Cl]PF6 {Cp∗ = C5Me5, M = Rh (10), Ir (11)}. All these complexes were

characterized by CHN analysis, IR, NMR and mass spectrometry besides

confirmation by single crystal X-ray diffraction studies for some representative

108

complexes355

as their hexafluorophosphate salts [3]PF6, [5]PF6, [8]PF6 and [10]PF6

(LVII).

N

N

S

N N

PF6

M=Ru, X=ClM=Rh, X=Cl

M=Ru, X=Br

M=Ru, X=Cl

M=Ir, X=Cl

=

=

=

=

=

M

X

(LVII)

(v) Complexes with other nitrogen and sulphur donor ligands

Ruthenium(III)-EDTA reacts with the 2-mercaptionicotinic ligand in aqueous

solution yielding a red product. In the presence of two time excess of the Ru(III)-

EDTA a binuclear species is formed involving two bidentate N, S and S, O

coordination modes.356

The synthesis and characterization of ruthenium complex

containing the chelating ligands N,N’bis(phenyl methylene)-1,2-ethylenediamine

(N,N), 2-pyridinethiol (NS), N,N-bis-(2-(dimethylamino)ethyl)-N,N’ dimethyl-1,2-

ethanediamine (N-crab), acetylacetonate and tetramethylethylenediamine is

described.357

109

The chemical behavior of triazole, thiadiazole and triazoline derivatives of

thiocarbohydrazide toward cis-[RuCl2(DMSO)4] was studied. This is probably the

first report358

of ruthenium(III) complex with a N-N-C-S chelating system. The

synthesis characterization and electrochemical properties of N3S2- ligated metal

complex of ligand 4, 10-dithia 1,7,13-triazabicyclo[11.3.3]nondecane are described.

Chelation of N3S2 donor ligand to He reactor produced radionuclide, rhodium(III)

gave359

a single product in high yield. Transition metal complexes of 5-benzoylbenzo-

1,2,3-triazole and 5-benzoyl benzimidazole thiosemicarbazone were prepared and

characterized.360

Chloro complexes of rhodium(III) with 2,5-butoxymethyl/ ethoxymethyl

substituted derivative of ethylene thiourea were synthesized and studied.361

New

complexes of rhodium(III) and ruthenium(III) with 1H-1,2,4-triazole-3-thiol were

prepared and characterized by spectroscopy.362

Lusty et al.363

reported that N-S

bidentate, 6-methyl-2-thiouracil forms [Rh(L)3]Cl3 (LVIII) in which thiouracil is

bonded through the S and the N to form four membered chelate rings, rather then S

and N-1.

N NH

Me

SH

Rh

OH

3

(LVIII)

110

Reaction of RhCl3∙3H2O with 4-amino-3,5-mercapto-1,2,4-triazole (H2TZ)

leads to two incompletely characterized364

complex a brick red solid identified as

[Rh(HTZ)2Cl(H2O)] and an orange red [Rh2(TZ)3]. The rhodium(III) complexes

containing 2-thiopyridone(pySH) and its conjugate anion 2-thiopyridonato(pySH) as

the only ligands, [Rh(PyS)2(PySH)2]Cl, [Rh(pyS)3(PySH)] and [Rh(pyS)3] react with

the tertiary phosphines Pme2Ph3, Ph2PCH2PPh2(dppm) and Ph2PCH2CH2PPh2 (dppe)

to give mixed py/ S tertiary phosphine complexes365

of the type [Rh(pyS)3L] (LIX)

and [Rh(pyS)2L2]ClO4 (LX).

Rh

S

NH

PMe2Ph

N

S

S N

Rh

S

PMe2Ph

N

S

S N

PMe2Ph

(LIX) (LX)

Three new Schiff bases of N-substituted isatin LI, LII, and LIII = Schiff base

of N-acetylisatin, N-benzylisatin, and N-benzoylisatin, respectively and their metal

complexes C1a,b = [Co2(LI)2Cl3]Cl, C2 = [Ni(LI)2Cl2]0.4BuOH, C3 =

[CuLICl(H2O)]Cl·0.5BuOH, C4 = [Pd(LI)2Cl]Cl, C5 =

[Pt(L1)2Cl2]Cl2·1.8EtOH.H2O, C6a = [CoLIICl]Cl ·0.4H2O·0.3DMSO, C6b =

[CoLIICl]Cl·0.3H2O·0.1BuOH, C7 = [NiLIICl2], C8 = [CuLII]Cl2·H2O, C9 =

[Pd(LII)2]Cl2, C10 = [Pt(LII)2.5Cl]Cl3, C11a = [Co(LIII)]C12·H2O, C11b =

[Co(LIII)]Cl2·0.2H2O, and C12 = [Ni(LIII)2]Cl2, C13 = [Ni(LIII)2]Cl2 were reported.

The complexes were characterized by elemental analyses, metal and chloride content,

111

spectroscopic methods, magnetic moments, conductivity measurements and thermal

studies. Some of these compounds were tested as antibacterial and antifungal agents

against Staphylococcus aureus, Proteus vulgaris, Candida albicans and Aspergillus

niger.366

The present work describes the synthesis and spectral properties of some

platinum metals chlorides coordination compounds of 4[N-(-(furan-2-

carboxalidene)amino]antipyrine thiosemicarbazone (FFAAPTS) and 4[N-(3, 4 , 5-

trimethoxybenzalidene)amino]antipyrine thiosemicarbazone (TMBAAPTS). All the

compounds have the general composition MCl2(L) (M = Pd2+

or Pt2+

; L = FFAAPTS

or TMBAAPTS) or MCl3(L) (M = Ru3+

, Rh3+

or Ir3+

; L = FFAAPTS or

TMBAAPTS). All the complexes were characterized by elemental analyses, molar

conductance, molecular weight, magnetic measurements, and infrared and electronic

spectra. The infrared spectra suggest that both the thiosemicarbazones behave as

neutral tridentate (N,N,S) ligands. The magnetic and electronic spectra suggest that

Pd2+

and Pt2+

complexes are square planar, while Ru3+

, Rh3+

and Ir3+

complexes have

octahedral geometry. On the basis of above studies, we tentatively assigned the

following structures of the present complexes.367

Ruthenium(III)–EDTA react with the 2-mercaptonicotinic ligand in aqueous

solution yielding a red product. In the presence of two time excess of the Ru(III)–

EDTA a binuclear species is formed involving two bidentate N, S and S, O

coordination modes. The synthesis and characterization of RuTp complex containing

the chelating ligands N,N’bis(phenyl methylene)-1,2-ethylenediamine(N,N), 2-

pyridinethiol (NS), N, N-bis-(2-dimethylamino)ethyl)-N,N’ dimethyl-1,2-

112

ethanediamine (N-crab), acetylacetonate and tetramethylethylenediamine is

described.368

Synthesis of several new octahedral binuclear ruthenium(III) complexes of the

general composition [(EPh3)2(X)Ru-L-Ru(X)(EPh3)2] containing benzene

dithiosemicarbazone ligands (where E = P or As; X = Cl or Br; L = binucleating

ligands) is presented. All the complexes have been fully characterized by elemental

analysis, FT-IR, UV-vis and EPR spectroscopy together with magnetic susceptibility

measurements. IR study shows that the dithiosemicarbazone ligands behave as

dianionic tridentate ligands coordinating through the oxygen atom of the deprotonated

phenolic group, nitrogen atom of the azomethine group and thiolate sulphur. In DMF

solution, all the complexes exhibit intense d-d transition and ligand-to-metal charge

transfer (LMCT) transition in the visible region. The magnetic moment values of the

complexes are in the range 1.78-1.82 BM, which reveals the presence of one unpaired

electron on each metal ion. The EPR spectra of the liquid samples at LNT show the

presence of three different 'g' values (gx≠gy≠gz) indicate a rhombic distortion around

the ruthenium ion. All the complexes exhibit two quasi-reversible one electron

oxidation responses (Ru(III)-Ru(III)/ Ru(III)-Ru(IV); Ru(III)-Ru(IV)/ Ru(IV)-

Ru(IV)) within the E 1/ 2 range of 0.61-0.74 V and 0.93-0.98 V respectively,369

versus Ag/ AgCl (LXI).

R

N

Ru

N

O EPh3

XEPh3

S

HN

YR

N

Ru

N

OPh3E

X Ph3E

S

NH

113

(LXI)

2.6. Complexes of ruthenium(III), rhodium(III) and iridium(III) with nitrogen

donor and nitrogen and oxygen donor macrocyclic complexes

The chemistry of ruthenium porphyrins has been reviewed.370,371

Reaction of

RuCl3 with H2TPP (H2TPP = meso-tetraphenylporphyrin) (LXII) in refluxing

ethanol/ acetic acid under CO for 21 hours yields an orange product originally

formulated372

as [Ru(III)(TPP)(CO)] with the vCO stretching vibration occurring near

1955 cm-1

.

NH

N HN

N

(LXII)

114

Oxidation of [Ru(porph)l2] (porph = OEP, TPP, L = PPh3, PBu3) afforded373

the ruthenium(III) species [Ru(porph)L2]+ which converts to [Ru(porph)BrL2] in the

presence of Br-. Treatment of [Ru(OEP)py2] with KCN over a prolonged period

affords [Ru(III)(OEP)(CH)2]- which can be converted to [Ru(OEP)(CN)py] on the

reaction with py.374

A range of octahedral ruthenium(III) complexes incorporating

tetraaza macrocyclic ligands have been synthesized.375,376

Reaction of [RuCl5(OH2)]2-

with L ((LXIII) & (LXIV) in alcoholic solvent under reflux affords trans-

[RuCl2(L)]+.

NH NH

NH NH

NH NH

NH NH

(LXIII) (LXIV)

Synthesis of Cis-[RuIII

Cl2(Cyclam)]Cl (cyclam = 1,4,8,11, tetraaza

cyclotetradecane) resulting in formation of macrocyclic complex.377

18-crown-6 ether

adducts were isolated for ruthenium(II) and ruthenium(III) ammine complexes and a

mixed valence binuclear ammine complex.378

A bis (tosylamido) ruthenium(III)

complex of 1,4,7-tri-me-1,4,7 = triazacyclononane (Me3tacn) was prepared and

characterized by X-ray.379

Fourteen ruthenium(III) compounds of Schiff bases and

macrocyclic ligands were prepared380

and found to be electroactive, exhibiting metal-

centered Ru(IV)

Ru(III)

couple.

115

Complexes of ruthenium(III) and rhodium(III) with 3 new tetraaza

macrocyclic ligands, tribenzo[b, f, j] [1,4,8,11] tetraazacyclotetradecane 5,9,10,14-

tetraone (OXO4bzO3)[14]-triene-N4[TBTAC14Tone], dibenzo(e,m) [1,4,8,11]

tetraazacyclotetradecanne-2,3,7,12-tetraone (OxO4bzO2)[14]-diene-N4,

[DBTAC14Tone] and dibenzo[e,n] [1,4,8,12] tetraazacyclotetradecane-2,3,713-

tetraone (OxO4-bzO2)[15]-diene-N4,[DBTAC15Tone]) were prepared and

characterized.381

The synthesis and characterization of rhodium two facile hindered porphyrins

are reported.382

The synthesized complexes are represented as-[e-

BHP(C12)2RhIII

(L)(H2O)]Cl, [e-BHP(C12)2RhIII

(L)(Cl)].

Several mononuclear N4-macrocyclic rhodium(III) hydrides were prepared

and characterized as {trans-(Cl)(14)aneN4RhH}2 (ZnCl4)DMSO.383

Rodium(III)

coordination compound with 5,17,12,14-tetramethyldibenzo [b, i] 1,4,8,11-

tetraaza[14] annulene (H2L) were synthesized384

as [Rh(III)L(23TTe˜)(CH3CN)Cl]Cl,

[Rh(III)L(24TTe˜)(CH3CH)Cl] and [Rh(III)L(22TTe˜)Cl]Cl2.

Treatment of [RhCl3[Me3[9]aneN3)](Me[9]ane N3 = 1,4,7-trimethyl-1,4,7-

triazacyclononane] with Ag(CF3SO3) in a 1:3 ratio that gives [RhCl3(Me3)[9]aneN3]2

Ag2(CF3SO3)(SO3)(MeCN) with novel Rh2Ag2Cl6 core.385

Three triazacyclononane bearing penent alkenyl group, 1,4,7-tri(4-pentynyl)-

1,4,7-triazacyclononanes(PPtacn), 1,4,7-tri(4-hexynyl)-1,4,7-triazacyclononane(4htanc)

were synthesized.386

Rhodium(III) porphyrin compounds (H2Porph = 2,8,12,18-tetrahexyl

3,7,13,17-tetramethyl-5,15-diphenyl porphine) with bridging hydrazine and

116

substituted hydrazine ligands were formed.387

Rhodium(III) complex with

macrocycle, meso-5-12-dimethyl-7-14-diphenyl-1,4,8,8,11-tetraazacyclotetradeco-

4,11-diene (L) (LXV) of the type trans-[RhCl2(L)]CIO4 has been reported.388

NH N

NH N

Ph Me

PhMe

(LXV)

Amino and alkyl rhodium derivates of meso-tetraphenyl-porphyrin (H2TPP)

and octaethylporphyrin (H2OEP) have been synthesized by reacting macrocycle with

rhodium trichloride in different alkyl amides and they were characterized389

with

formula [RhTPP(DMA)Cl], [EtRhTPP], [RhTPP(MMA)2X], [RhTPP(MEA)2Cl].

[RhOEP(DMA)Cl], [EtRHOEP], [RhOEP(MMA)2Cl] and [RhOEP(MEA)2Cl].

The properties of the cyclam, cyclen and 1-(3-propyl ammonium) complexes

of Ru(II/ III), [Ru(macrocycle)LL’]n+

and related species are reviewed.390

L and L’

are ligands such as chloro, aqua, hydroxo, amides, pyridines and imides.

Ruthenium(III) compounds of tetraaza Schiff bases macrocycles derived from

o- or m-phenylenediamine and acetylacetonate or glyoxal, were synthesized by

template method. The complexes are [M’LCl2]Cl [M’ = Ru], L = 1.5:11, 15-

dimetheno-2,4,10,12-tetramethyl-[1,5,9,13] tetrazazcyclohexadeca-

1,3,5,6,10,11,13,15,16,20-decene (L1) (LXVI) 1,5:10,14-dimetheno

117

[1,4,8.11]tetraazacyclotetradeca-3,5,6,8,10,12,14,15,17-decene (L2) and dibenzo-[b,i]-

8,10,19,21-tetramethyl [1,5,8,12]-tetraazacyclotetradeca-1,3,5,7,10,12,14,16,18,21-

decene(L3) (LXVII) were prepared.391

the ruthenium(III) complexes (LXVIII) and

(LXIX) are six coordinated and octahedral.

NN

C

C N N

(LXVI)

NN

C

C N N

(LXVII)

118

NN

C

C N N

MCl CICI

(LXVIII)

NN

C

C N N

MClCI

(LXIX)

Reaction of RhCl3 (M = Rh(III) with Schiff base derived from 2-

phenylenediamine and 2-aminobenzaldehyde were studied in ethanol and

[M(SB)Cl2]Cl (LXX) were isolated.392

119

NN

C

C N N

R

R'

R'

MClCI

CI

(LXX)

Complexes of ruthenium(III) and rhodium(III) with three new tetraaza

macrocyclic ligands (L), tribenzo (b, f, I) [1,4,8,11] tetraazacyclotetradecane-

5,9,10,14 tetraone, dibenzo (e,m) [1,4,8,12] tetraone and dibenzo (e,m) [1,4,8,11]

tetraazacyclotetradecane-2,3,7,12-tetraone have been prepared393

and characterized

with genera formula [RuLCl2]Cl3∙H2O and [RhLCl2]Cl2∙H2O.

The first synthesis and electrochemistry of metalloporphyrins containing a

bound PF3 axial ligand has been achieved. The investigated compounds are

[Ru(por)(PF3)] where por is the dianion of 5,10,15,20-tetraphenyl, tetra(p-

bromophenyl), tetra(p-methoxyphenyl), 2,7,12,17-tetraethyl-3,8,13,18-tetramethyl- or

2,3,7,8,12,13,17,18-octaethyl-porphyrin. Each [Ru(por)(PF3)] species was

investigated with respect to its spectroscopic and electrochemical properties and the

resulting data compared with those for [Ru(por)(CO)] having the same porphyrin ring.

A number of similarities exist between the carbonyl and PF3 derivatives in methylene

chloride but major differences can be observed in other non-aqueous solutions. The

first reduction of each complex is reversible in tetrahydrofuran (thf) and leads to a

120

porphyrin π-anion radical rather than a ruthenium(I) species as identified by UV/ VIS

spectroelectrochemistry. Each investigated complex also undergoes two reversible

oxidations in dichloromethane, the first of which leads to a porphyrin π-cation radical.

The [Ru(por)(PF3)] derivatives appear to be more stable than the [Ru(por)(CO)]

analogues in thf or CH2Cl2, but an electrochemically initiated conversion of

[RuII(por)(PF3)(py)] into [Ru

III(por)(py)2]

+ can be readily accomplished in pyridine

(py) or CH2Cl2–pyridine mixtures. This type of reaction has never been seen upon

oxidation of a ruthenium(II) porphyrin and was monitored by cyclic voltammetry and

UV/ VIS spectroelectrochemistry.394

The coordination compounds of PdII, Pt

II, Rh

III and Ir

III metal ions with a

Schiff base ligand (L) i.e. 2,6- diacetylpyridine bis(thiosemicarbazone) have been

synthesized and characterized by elemental analyses, molar conductance, magnetic

susceptibility measurements, IR, NMR and electronic spectral studies. On the basis of

molar conductance and elemental analyses the complexes were found to have

composition [M(L)]Cl2 and [M’(L)Cl]Cl2, where M = Pd(II), Pt(II) and M’ = Rh(III),

Ir(III). The spectral studies reveal that the complexes possess monomeric

composition. Complexes of PdII and Pt

II were found to have four coordinated square

planar geometry whereas the complexes of RhIII

and IrIII

posses six coordinated

octahedral geometry. The ligand field parameters were calculated using various

energy level diagrams. In vitro synthesized compounds and metal salts have been

tested against some species of plant pathogenic fungi and bacteria in order to assess

their antimicrobial properties (LXXI, LXXII).395

121

NC C

CH3 CH3

N N

NHNH

C CS S

NH2NH2

M

Cl2

NC C

CH3 CH3

N N

NHNH

C CS S

NH2NH2

M

Cl2

Cl

(LXXI) ( LXXII)

Palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes of

general stoichiometry [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl are

synthesized with a tetradentate macrocyclic ligand, derived from 2,6-diaminopyridine

with 3-ethyl 2,4-pentanedione. Ligand was characterized on the basis of elemental

analyses, IR, mass and 1H NMR and

13C NMR spectral studies. All the complexes

were characterized by elemental analyses, molar conductance measurements,

magnetic susceptibility measurements, IR, mass, electronic spectral techniques and

thermal studies. The value of magnetic moments indicates that all the complexes are

diamagnetic except ruthenium(III) complex which shows magnetic moments

corresponding its one unpaired electron. The macrocyclic ligand and all its metal

complexes were also evaluated in vitro against some plant pathogenic fungi and

bacteria to assess their biocidal properties (LXXIII).396

122

N

N

N

CH

N

CH2CH3

N

N

CH3CH2

H3C

H3C

Cl

Cl

CH3

CH3

M

M = Ru(III), Ir(III)

HC

(LXXIII)

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-

tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-

1(22),2,5,7,9,11,13,16,18,20-decaene(L) has been synthesized and characterized by

elemental analyses, IR, Mass, and 1H NMR spectral studies. Complexes of

palladium(II), platinum(II), ruthenium(III) and iridium(III) have been prepared and

characterized by elemental analyses, molar conductance measurements, magnetic

susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the

basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2,

[Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common

solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in

DMF/ DMSO. The value of magnetic moment indicates that all the complexes are

diamagnetic except ruthenium(III) complex which shows magnetic moment

123

corresponding to one unpaired electron. The magnetic moment of ruthenium(III)

complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and

its complexes have been screened in vitro, as growth inhibiting agents. The antifungal

and antibacterial screening were carried out using Food Poison and Disc Diffusion

Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium

oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The

compounds were dissolved in DMSO to get the required solutions. The required

medium used for these activities was PDA and nutrient agar (LXXIV), (LXXV).397

N

H2C

N

N N

CH3H3C

M

C C

CH2

H3C CH3

+2

N

H2C

N

N N

CH3H3C

M

C C

CH2

H3C CH3

+

Cl

Cl

M = Ru(III), Ir(III)

(LXXIV) (LXXV)

The reaction of furfurylamine with two equivalents of PPh2Cl in the presence

of Et3N affords furfuryl-2-(N,N-bis(diphenylphosphino)amine), (Ph2P)2NCH2-C4H3O

(1). The corresponding ruthenium(II) complex trans-[Ru((PPh2)2NCH2-C4H3O)2Cl2]

(3) was synthesized by reacting 1 with [Ru(η6-p-cymene)(μ-Cl)Cl]2. The reaction of

furfurylamine with one equivalent of PPh2Cl gives Ph2PNHCH2-C4H3O (2). The

reaction of 2 with [Ru(η6-p-cymene)(μ-Cl)Cl]2, [Ru(η

6-benzene)(μ-Cl)Cl]2, [Rh(μ-

Cl)(cod)]2 and [Ir(η5-C5Me5)(μ-Cl)Cl]2 yields the complexes [Ru(Ph2PNHCH2-

C4H3S)(η6-p-cymene)Cl2] (4), [Ru(Ph2PNHCH2-C4H3O)(η

6-benzene)Cl2] (5),

[Rh(Ph2PNHCH2-C4H3O)(cod)Cl] (6) and [Ir(Ph2PNHCH2-C4H3O)(η5-C5Me5)Cl2]

124

(7), respectively. All the complexes were isolated from the reaction solution and fully

characterized by analytical and spectroscopic methods. The structure of

[Ru(Ph2PNHCH2-C4H3O)(η6-p-cymene)Cl2] (4) was also determined by single crystal

X-ray diffraction. Complexes 3–7 are suitable precursors forming highly active

catalysts in the transfer hydrogenation of a variety of simple ketones. Notably, the

catalysts obtained by using the ruthenium complexes [Ru(Ph2PNHCH2-C4H3O)(η6-p-

cymene)Cl2] (4) and [Ru(Ph2PNHCH2-C4H3O)(η6-benzene)Cl2] (5) are much more

active in the transfer hydrogenation, converting the carbonyls to the corresponding

alcohols in 97–99% yields (TOF ≤ 300 h−1

), compared to analogous rhodium and

iridium complexes and the trans-Ru(II)-p-cymene bis(phosphino)amine complex.398

Reaction of [(p-cymene)RuCl2(PPh3)] (1) or [Cp∗MCl2(PPh3)] (Cp∗ = C5Me5)

(3a: M = Rh; 4a: M = Ir) with 1-alkynes and PPh3 were carried out in the presence of

KPF6, generating the corresponding alkenyl-phosphonio complexes, [(p-

cymene)RuCl(PPh3){CH=CR(PPh3)}](PF6) (2a: R = Ph; 2b: R = p-tolyl) or

[Cp∗MCl(PPh3){CH-CPh(PPh3)}](PF6) (5: M = Rh; 6: M = Ir). Similar reactions of

complexes [Cp∗RhCl2(L1)] (3a: L

1 = PPh3; 3c: L

1 = P(OMe)3) with L

2 (L

2 = PPh3,

PMePh2, P(OMe)3) gave [Cp∗RhCl(L1)(L

2)](PF6) (7bb: L

1 = L

2 = PMePh2; 7ca:

L1 = P(OMe)3, L

2 = PPh3; 7cc: L

1 = L

2 = P(OMe)3). Alkenyl-phosphonio

complex 5 was treated with P(OMe)3 or 2,6-xylyl isocyanide, affording

[Cp∗RhCl(L){CH=CPh(PPh3)}](PF6) (8a: L = P(OMe)3; 8b: L = 2,6-xylNC). X-ray

structural analyses of 2a, 6 and 8a revealed that the phosphonium moiety bonded to

the Cβ atom of the alkenyl group are E configuration.399

Several new electrophilic metal isocyanide complexes have been fully

characterized and reported here. Isocyanide induced cleavage of the dimer,

125

[LMCl2]2 {LM = Cp∗Ir, Cp∗Rh, or (p-cymene)Ru}, with 2,6-xylylisocyanide or 2,6-

diethylphenylisocyanide produces complexes of the general formula LM(CNAr)Cl2.

Halide metathesis of the dichloro complexes with sodium iodide produces the

corresponding complexes with the general formula LM(CNAr)I2. For the analogous

ruthenium complexes better results were achieved via isocyanide induced cleavage of

[(p-cymene)RuI2]2 and was synthesized differently from previous reports. Several

neutral complexes in reaction with AgPF6 in acetonitrile form cationic, solvent-

coordinated complexes have been fully characterized. Most reactions with rhodium

decomposed to either [Cp∗RhCl(MeCN)]2[(PF6)2] starting from the dichloro

complexes or [Cp∗Rh(MeCN)3,(PF6)2] and Cp∗Rh(CNAr)I2 starting from the diiodo

complexes.400

Several bases were probed to see if cyclization could be induced, but

were not successful in any case. Many of these complexes have been characterized by

single crystal X-ray crystallography.

2.7. Object of the Present Work

A perusal of literature regarding the synthesis and characterization of

derivatives of ruthenium(III), rhodium(III) and iridium(III) reveals that little systematic

work have been carried out on multidentate ligands containing nitrogen, oxygen and

sulphur donor atom. Therefore, it has been worthwhile to study the coordination

behavior of such type of multidentate ligands towards ruthenium(III), rhodium(III) and

iridium(III). The complexes have been characterized on the basis of elemental analysis,

electrical conductance, magnetic susceptibility measurements, spectral (electronic,

infrared and 1H NMR) data, FAB mass and thermal analyses. The main results obtained

during the course of present investigation can be summarized under the following

heading:

126

(1) RUTHENIUM(III) COMPLEXES WITH SCHIFF BASES DERIVED FROM

ISATIN AND VARIOUS SULPHA DRUGS

(2) RUTHENIUM(III) COMPLEXES WITH SCHIFF BASE DERIVED FROM

SULPHA DRUGS AND VARIOUS ALDEHYDES

(3) RUTHENIUM(III) AND RHODIUM(III) COMPLEXES WITH SCHIFF

MANNICH BASES DERIVED FROM SUBSTITUTED ISATIN AND

DITHIOOXAMIDE

(4) RUTHENIUM(III) AND IRIDIUM(III) COMPLEXES WITH HYDRAZONES

DERIVED FROM ISONICOTINOYL HYDRAZIDE AND VARIOUS

ALDEHYDES/ KETONES

(5) RUTHENIUM(III) COMPLEXES WITH SCHIFF BASES DERIVED FROM

SUBSTITUTED MERCAPTOTRIAZOLES AND PYRIDINE-2-

CARBOXALDEHYDE/ THIOPHENE-2-CARBOXALDEHYDE

127

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391. S. Chandra, K. Gupta and N. Sangeetika, Synth. React. Inorg. Met.-Org.

Chem., 32, 545, 2002.

392. V. K. Sharma, O. P. Pandey and S. K. Senguppta, Bull. Soc. Chim. Fr., 469,

1991.

393. S. J. Swamy, B. V. Pratap, P. Someshwar, K. Suresh and D. Nagaraju, J.

Chem. Res., 5, 313, 2005.

149

394. K. M. Kadish, Y. Hu, P. Tagliatesta and T. Boschi, J. Chem. Soc., Dalton

Trans., 1167, 1993.

395. M. Tyagi and S. Chandra, Open J. Inorg. Chem, 2, 70, 2012.

396. S. Rani, S. Kumar and S. Chandra, Spectrochim. Acta A, 78, 1507, 2011.

397. S. Rani, S. Kumar and S. Chandra, Spectrochim. Acta A, 118, 244, 2014.

398. C. Kayan , N. Meric, M. Aydemir, A. Baysal, D. Elma, B. Ak, E. Şahin,

N. Gurbuz and I. Ozdemir, Polyhedron, 42, 142, 2012.

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360, 3296, 2007.

400. A. P. Walsh, W. W. Brennessel and W. D. Jones, Inorg. Chim. Acta, 407,

131, 2013.

150

CHAPTER 3

3. Experimental

This chapter includes the details regarding the materials used, synthetic

procedure adopted for the preparation of ligands and their complexes. The preparation

of precursors has revealed as industrial importance. The detailed descriptions of the

present study and selection about the specific materials have been considered as well

as experimental equipment applied for the preparation of ligands. The technical

specification as physicochemical techniques employed for the characterization of the

ligands and their metal complexes are also given.

Apparatus

All the glass apparatus fitted with interchangeable joints were used throughout

the work. The apparatus were well cleaned before experiment start and well dried in

electric oven at 120-140˚C for minimum 3 to 4 hours. The filtration processes were

used in G-3 and G-4 sintered crucible wash with alcohol before use. Condenser, round

bottom flask one neck or two neck with standard joint were used. Weighing tubes and

pipettes made of standard joints were used. Weighing balance, weighing tube cleaned

in proper way, melting point of the compounds were determined with the help of

capillary tube and solubility test taken in test tube which was rinsed with water and

always dried.

Materials

All the chemicals used in present work were of high purity and Analylitical

grade reagent (AR). All reagent grade solvents were purified by the standard

procedure. Alcohol was used in template reaction and excess of alcohol distilled by

151

the procedure reported in the literature1. RuCl3∙3H2O, RhCl3∙3H2O and IrCl3∙3H2O

and were purchased from E. Merck/ Loba Chemie/ Himedia and isatin dithiooxamide,

sulpha drugs and were purchased from E. Merck/ Sigma-Aldrich. Metal salts and all

solvents used were of standard /spectroscopic grade. Experimental points of view

their are some other solvent were used i.e. chloroform, acetone, tetrahydrofuran,

dimethylsulphoxide, dimethyl formamide and diethyl ether.

Preparation of ligands

3.1. Schiff bases derived from isatin and various sulpha drugs

The preparation of ligands involve following two steps:

(i) Preparation of isatin

Isatin was prepared by previously reported procedure of Hassaan2. In 5L round

bottom flask chloral hydrate (90 g, 0.54 mol) and 1200 cm3 of water is taken. To this

130 g of crystalline sodium sulphate and a solution of (0.5 mol) aniline added. A

concentrate hydrochloric acid has been added to dissolve the amine, and finally a

solution of 110 g of hydroxylamine hydrochloride in 500 cm3 of water. The flask was

heated over a wire gauge, so that vigorous boiling began in about 40 min. After 1-2

minutes of vigorous boiling reaction was completed. During the heating period some

crystals of isonitrosoacetanilide separated out, on cooling the solution in running

water, the remainder crystallized. It was then filtered with suction and air dried.

Yield was 50-65%

Cyclization of isonitrosoacetanilide to isatin is done as concentrate sulphuric

acid(163 cm3, Sp. Gr. 1.84) was warmed to 50˚C in 1L round bottom flask with an

efficient mechanical stirrer. To this 0.23 mol of dry isonitrosoacetanilide was added as

152

such a rate as to keep the temperature between 60-70˚C, external cooling was applied

at this stage so that reaction can be carried out more rapidly. After the addition of the

isonitrosoacetanilide the reaction was heated at 80˚C and kept at this temperature for

about 10 minutes. Then reaction mixture was cooled at room temperature and poured

upto 10-12 times its volume of cracked ice. After standing for half an hour the isatin

was filtered with suction, washed several times with cold water to remove sulphuric

acid and then dried in air.

Yield of crude isatin was 55-60%

For the purification, crude isatin (50 g) was suspended in 250 cm3 of hot water

and treated with a solution of 50 cm3 of 44% sodium hydroxide. The solution was

stirred mechanically and isatin passed into the solution. Dilute hydrochloric acid was

then added with stirring until a slight precipitate appeared. This required about 70-75

cm3 of acid (2 N). The mixture was filtered at once the precipitate was rejected and

filtrate was made acidic with hydrochloric acid. The solution is then cooled rapidly

and the isatin that separated was filtered with suction and dried in air.

(ii) Preparation of Schiff bases derived from isatin and various sulpha drugs

Schiff base was prepared by reported procedure given in literature.3

Corresponding the Schiff bases (LH) were prepared by condensing equimolar

quantities of isatin with various sulpha drugs in ethanol containing a few drops of

concentrated hydrochloric acid. The reaction mixture was poured in crushed ice where

precipitate is obtained. It was filtered off, washed from ethanol and finally dried. A

template reaction was carried out to synthesize the Schiff base ligands. The activity of

ligands was strongly dependent upon the nature of the heteroaromatic rings. A

solution of isatin (0.588 g, 0.02 mol) in ethanol (20 ml) was added to solution of

153

sulphanilamide (0.688 g, 0.02 mol)/ sulphamerazine (1.056 g, 0.02 mol)/

sulphaguanidine (0.856 g, 0.02 mol)/ sulphacetamide (0.856 g, 0.02 mol)/

sulphadiazine (0.01 g, 0.02 mol) or sulphapyridine (0.998 g, 0.02 mol) in ethanol. The

reaction mixtures were then refluxed for 10-12 hrs with constant stirring. The residual

product was obtained and separated out and washed with ethanol and diethyl ether.

The proposed structures of the Schiff base ligands are known to be good agreement

with the ratios concluded from analytical data.

Yield was 40-65%

The physical properties and analytical data are included in Table 3.I.

154

Table: 3.I. Physical and analytical data of the Schiff bases derived from isatin and various sulpha drugs.

Compounds

Empirical formula

Colour M.P. (ºC) Yield

(%)

Analysis found (calcd.)%

C H N S

IShAH

C14H14N3SO 3

Orange 240 57 54.99

(55.80)

3.22

(3.67)

12.22

(13.94)

9.94

(10.64)

IShMH

C19H15N5SO3

Cream 220 59 57.72

(58.00)

3.12

(3.84)

16.62

(17.80)

7.88

(8.14)

IShGH

C15H13N5SO3

Orange 254 64 51.42

(52.47)

3.01

(3.81)

19.46

(20.39)

8.93

(9.33)

IShDH

C18H13N5SO3

Orange 185 40 55.25

(56.98)

3.42

(3.45)

17.80

(18.45)

7.10

(8.45)

IShAcH

C16H13N3SO4

Orangish yellow 135 52 55.60

(56.96)

3.70

(3.81)

11.85

(12.23)

8.75

(9.33)

IShPH

C19H14N4SO3

Cream 140 54 59.10

(60.30)

3.52

(3.72)

14.20

(14.80)

7.25

(8.47)

155

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

156

3.2. Schiff bases derived from aldehydes and various sulpha drugs

Schiff bases were prepared by reported procedure given in literature.4

(i) o-Vanillin sulphanilamide (oVSaH)

Ethanolic solution of o-Vanillin (3.04 g, 0.02 mol) was added to methanolic

solution of sulpha drug, Sulphanilamide (3.44 g, 0.02 mol) and the resulting mixture

was then refluxed on a water bath for 4-5 hours. The colored solid mass separated out

on cooling, which was kept in a refrigerator for better crystallization. It was then

filtered, washed with ethanol, ether and subsequently dried over anhydrous calcium

chloride in desiccators.

Yield was 70%

(ii) o-Vanillin sulphamerazine (oVSmrzH)

Ethanolic solution of o-Vanillin (3.04 g, 0.02 mol) was added to methanolic

solution of sulpha drug, Sulphamerazine (5.28 g, 0.02 mol) and the resulting mixture

was then refluxed on a water bath for 4-5 hours. The colored solid mass separated out

on cooling, which was kept in a refrigerator for better crystallization. It was then

filtered, washed with ethanol, ether and subsequently dried over anhydrous calcium

chloride in desiccators.

Yield was 76%

(iii) Salicylaldehyde sulphanilamide (SdSaH)

Salicylaldehyde (2.1 ml, 0.02 mol) was added to methanolic solution of sulpha

drug, Sulphanilamide (3.44 g, 0.02 mol) and the resulting mixture was then refluxed

on a water bath for 4-5 hours. The colored solid mass separated out on cooling, which

157

was kept in a refrigerator for better crystallization. It was then filtered, washed with

ethanol, ether and subsequently dried over anhydrous calcium chloride in desiccators.

Yield was 74%

(iv) Salicylaldehyde sulphamerazine (SdSmrzH)

Salicylaldehyde (2.1 ml, 0.02 mol) was added to methanolic solution of sulpha

drug, Sulphamerazine (5.28 g, 0.02 mol) and the resulting mixture was then refluxed

on a water bath for 4-5 hours. The colored solid mass separated out on cooling, which

was kept in a refrigerator for better crystallization. It was then filtered, washed with

ethanol, ether and subsequently dried over anhydrous calcium chloride in desiccators.

Yield was 67%

(v) 2-hydroxy-1-naphthaldehyde sulphanilamide (2hNSaH)

Methanolic solution of 2-hydroxy-1-naphthaldehyde (3.44 g, 0.02 mol) was

added to methanolic solution of sulpha drug, Sulphanilamide (3.44 g, 0.02 mol) and

the resulting mixture was then refluxed on a water bath for 4-5 hours. The colored solid

mass separated out on cooling, which was kept in a refrigerator for better

crystallization. It was then filtered, washed with ethanol, ether and subsequently dried

over anhydrous calcium chloride in desiccators.

Yield was 78%

(vi) 2-hydroxy-1-naphthaldehydesulphamerazine (2hNSmrzH)

Methanolic solution of 2-hydroxy-1-naphthaldehyde (3.44 g, 0.02 mol) was

added to methanolic solution of sulpha drug, Sulphamerazine (5.28 g, 0.02 mol) and

the resulting mixture was then refluxed on a water bath for 4-5 hours. The colored solid

158

mass separated out on cooling, which was kept in a refrigerator for better

crystallization. It was then filtered, washed with ethanol, ether and subsequently dried

over anhydrous calcium chloride in desiccators.

Yield was 46%

The physical properties and analytical data are included in Table 3.II.

159

Table: 3.II. Physical and analytical data of Schiff bases derived from sulpha drugs and various aldehydes.

Compound

Empirical formula

Colour

M.P. (ºC)

Yield (%)

Analysis found (calcd.)%

C H N S

OVSaH

C14H14N2SO4

Yellow 210 73 53.69

(54.89)

4.22

(4.61)

8.22

(9.14)

9.94

(10.47)

OVSmrzH

C19H18N4SO4

Orangish yellow 219 76 56.72

(57.27)

4.12

(4.55)

13.62

(14.06)

7.88

(8.05)

SdSaH

C13H12N2SO3

Fine yellow 226 74 55.42

(56.51)

4.01

(4.38)

9.46

(10.14)

10.93

(11.6)

SdSmrzH

C18H16N4SO3

Yellow 234 67 57.25

(58.68)

3.92

(4.38)

14.80

(15.21)

8.10

(8.70)

2hNSaH

C17H14N2SO3

Canary yellow 278 78 61.60

(62.62)

3.90

(4.32)

7.85

(8.59)

8.75

(9.82)

2hNSmrzH

C22H18N4SO3

Mustard yellow 227 46 62.10

(63.14)

4.22

(4.34)

13.20

(13.39)

7.25

(7.66)

160

Where,

oVSaH = Schiff base derived from sulphanilamide and o-Vanillin

oVSmrzH = Schiff base derived from sulphamerazine and o-Vanillin

SdSaH = Schiff base derived from sulphanilamide and salicylaldehyde

SdSmrzH = Schiff base derived from sulphamerazine and salicylaldehyde

2hNSaH = Schiff base derived from sulphanilamide and 2-hydroxy-1-naphthaldehyde

2hNSmrzH = Schiff base derived from sulphamerazine and 2-hydroxy-1-naphthaldehyde

161

3.3. Schiff mannich bases derived from various isatin and dithiooxamide

Schiff base mannich was prepared by reported procedure.5 The compound can

be alternatively named as iminoisatin. The Schiff mannich bases (LH) were prepared by

condensing equimolar quantities of isatin with Dithiooxamide in dry ethanol containing

2-3 drops of glacial acetic acid was heated under reflux for 10 hour with continuous

stirring. The mixture was then left at room temperature for 24 hrs. A colored precipitate

was obtained. It was filtered off, washed from ethanol and finally dried. A template

reaction was carried out to synthesize the ligands. The activity of ligands was strongly

dependent upon the nature of the heteroaromatic rings. A solution of morpholine isatin

(2.49 g, 0.01 mol)/ N,N- diphenylamine isatin (2.49 g, 0.01 mol)/ N-methyl isatin

(1.611 g, 0.01 mol)/ N-acetyl isatin (1.891 g, 0.01 mol), N-benzyl isatin (2.372 g, 0.01

mol) and dithiooxamide (1.021 g, 0.01 mol) in dry ethanol at room temperature. The

residual product was obtained and separated out and washed with ethanol and diethyl

ether.

Yield was 35-60%

The physical properties and analytical data are included in Table 3.III.

162

Table: 3.III. Physical and analytical data of the Schiff mannich bases derived from substituted isatin and dithiooxamide.

Compound

Empirical

formula

Colour M.P.(ºC) Yield (%) Analysis found (calcd.)%

C H N S

MrdtoII

C15H16N4S2O2

Red 140 25 50.99

(51.70)

4.22

(4.62)

15.22

(16.07)

9.94

(10.64)

DpdtoII

C23H18N4S2O

Brown 179 22 63.72

(64.16)

4.12

(4.21)

12.62

(13.01)

7.88

(8.14)

NMydtoII

C11H11N3S2O

Orange 260 22 51.42

(52.47)

3.01

(3.81)

19.46

(20.39)

8.93

(9.33)

NAydtoI

C12H11N3S2O2

Dark orange 255 27 55.25

(56.98)

3.42

(3.45)

17.80

(18.45)

7.12

(8.45)

NBydtoI

C17H13N3S2O

Orange 120 20 55.60

(56.96)

3.70

(3.81)

11.85

(12.23)

8.75

(9.33)

163

Where,

MrdtoII = Schiff mannich base derived from N-morpholino methylisatin and dithiooxamide

DpdtoII = Schiff mannich base derived from N-diphenylaminomethylisatin and dithiooxamide

NMydtoII = Schiff mannich bass derived from N-methylisatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetylisatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzylisatin and dithiooxamide

164

3.4. Schiff bases derived from (isoniazid) isonicotinoyl hydrazide and various

aldehydes/ ketones

Hydrazide have been prepared by general procedure reported in literature.6,7

The isoniazid (isonicotinylhydrazide) Schiff bases ligands (L1H2, L2H2, L3H2, L4H2)

were prepared by 1:1 condensation equimolar quantities of isoniazid (0.05 mol) with

various aldehydes/ ketones (0.05 mol) in ethanol (50 ml). Reaction mixture was

heated under reflux for 6 hours. A solution of isoniazide (6.857 g, 0.05 mol) in

ethanol (50 ml) was added to solution of aldehydes/ ketones viz., 2-

hydroxybenzaldehyde, o-vanillin, 2-hydroxyacetophenone, 5-chlorosalicylaldehyde

(0.05 mol) in ethanol. The residual product was obtained and separated out and

washed with ethanol and diethyl ether. The proposed structures of the Schiff base

ligands are known to be good agreement with the ratios concluded from analytical

data.

Yield was 75-99%

The physical properties and analytical data are included in Table 3.IV.

165

Table: 3.IV. Physical and analytical data of the hydrazones derived from isonicotinoyl hydrazide and aldehydes/ ketones.

Compounds

Empirical formula

Colour M.P. (ºC) Yield (%) Analysis found (calcd.)%

C H N Cl

HBINH

C13H11N3O2

Cream 220 79 63.99

(64.72)

4.42

(4.59)

16.22

(17.41)

-

o-VINH

C14H14N3O3

Cream 225 98 60.72

(61.98)

4.12

(4.83)

41.62

(42.02)

-

2-HAINH

C14H13N3O2

white 240 76 64.42

(65.87)

5.01

(5.13)

15.46

(16.46)

-

5-CSINH

C13H10N3O2Cl

cream 230 88 55.25

(56.63)

3.42

(3.65)

14.80

(15.24)

12.02

(12.44)

166

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

167

3.5. Schiff base derived from substituted mercaptotriazoles and pyridine-2-

carboxaldehyde/ thiophene-2-carboxaldehyde

The preparation of ligands involve following four steps:

(i) Preparation of esters

A mixture of 4-methoxybenzoic acid/ 2-hydroxybenzoic acid/ 2-

chlorobenzoic acid in absolute ethanol and concentrate sulphuric acid as a catalyst

was refluxed for 5-6 hours, on a steam bath set the apparatus for downward

distillation to distil of the excess ethanol and then cooled the flask. This was poured

slowly with continuous stirring in crushed ice. Ammonia solution was added to render

the resulting solution strongly alkaline. Thus, ester was extracted with ether and dried

over anhydrous MgSO4.

(ii) Preparation of hydrazides

The hydrazides were prepared by the method of Efimovsky et. al.8 A mixture

of hydrazine hydrate (1.0 mol) and appropriate ester was taken in ethanol. Refluxed

the mixture for 3-4 hours, distil off the ethanol and cool. Filter off the crystals of the

acid hydrazide and recrystallise from ethanol, dilute ethanol or from water.

(iii) Preparation of 4-amino-3-(4-methoxyphenyl/ 2-hydroxyphenyl/ 2-

chlorophenyl)-5-mercapto-1,2,4-triazoles9

The appropriate acid hydrazide (0.01 mol) was added to absolute alcohol (50

ml), containing KOH (1.6 g, 0.02 mol) at room temperature, CS2 was added (2.3 g,

0.013 mol) and the mixture stirred at room temperature for 10 hours. The mixture

diluted was diluted with ether (30 ml) and stirred for further 1 hour. The potassium

salt was used for the next stage without further purification. Hydrazine hydrate (99%

0.02 mol) was gradually added to the above potassium salt (0.01 mol) dissolved in

water (20 ml) with stirring and the mixture was refluxed gently for 3 hours during

168

which hydrogen sulphide evolved and the colour of the reaction mixture changed to

deep green colour. It was then cooled to 5˚C and acidified with conc. HCl to pH 1.0.

A yellow solid separated out which was filtered, washed with water and purified by

recrystallization from ethanol to afford the triazole.

Yield was 70-80%

(iv) Preparation of Schiff bases derived from 4-amino-3-(4-methoxyphenyl/ 2-

hydroxyphenyl/ 2-chlorophenyl)-5-mercapto-1,2,4-triazoles

These ligands were prepared according to the method reported in

literature.10,11

These were prepared by refluxing 4-amino-3-(4-methoxyphenyl/ 2-

hydroxyphenyl/ 2-chlorophenyl)-5-mercapto-1,2,4-triazoles (0.01 mol) with

appropriate aldehyde viz., pyridine-2-carboxaldehyde or thiophene-2-carboxaldehyde

in aq. ethanol (50%, 50 cm3) for 6-8 hours. The yellowish brown or white coloured

crystal were separated out which were filtered off, washed with ethanol, distilled

water and ether then dried in vacuum. This was recrystallised from ethanol.

Yield was 70-80%

The physical properties and analytical data of the Schiff bases derived from

substituted mercaptotrizoles are summarized in Table 3.V.

169

Table: 3.V. Physical and analytical data of the Schiff bases derived from substituted mercaptotriazoles and thiophene-2-carboxaldehyde

or pyridine-2-carboxaldehyde.

Compound Colour M.P. (ºC) Yield

(%)

Analysis found (calcd.)%

C H N S Cl

ATMTH

C14H12N4S2O

Light yellow 185 77 53.87

(53.14)

3.28

(3.82)

16.88

(17.78)

19.86

(20.26)

-

APMTH

C15H13N5SO

Yellowish green 140 60 57.00

(57.86)

4.14

(4.28)

21.64

(22.5)

9.88

(10.29)

-

STMTH

C13H10N4S2O

Pale yellow 240 87 51.66

(51.63)

3.12

(3.33)

17.98

(18.61)

20.86

(21.20)

-

SPMTH

C14H11N5SO

Mud green 260 30 55.78

(56.54)

3.24

(3.72)

22.82

(23.66)

9.98

(10.78)

-

CTMTH

C13H9N4SCl

Light green 145 42 53.87

(54.07)

3.02

(3.14)

18.21

(19.49)

10.40

(11.10)

12.02

(12.64)

CPMTH

C14H10N5SCl

Cream 190 50 52.87

(53.24)

3.10

(3.19)

21.89

(22.29)

10.62

(11.22)

11.94

(12.24)

170

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pyridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pyridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pyridine-2-carboxaldehyde

171

3.6. Analytical methods

Analytical chemistry has been important since the early days of chemistry,

providing methods for determining which elements and chemicals are present. During

this period significant analytical contributions to chemistry include the development

of systematic analysis and systematized organic analysis based on the specific

reactions of functional groups. The separation of components is often performed prior

to analysis. Analytical chemistry has played critical roles in the understanding of

basic science to a variety of practical applications. The prepared ligands and

complexes were aquarate results in quantitative and qualitative analysis.

Elemental analysis

Carbon and Hydrogen

Elemental analysis is a process where a sample of some material is analyzed.

Elemental analysis can be qualitative (determining what elements are present), and it

can be quantitative (determining how much of each are present). The analysis of

results is performed by determining the ratio of elements from within the sample, and

working out a chemical formula that fits with those results. The elemental analyses

were carried out on Carlo Erba 1108 elemental analyzer at SAIF, Central Drug

Research Institute, Lucknow, India.

Estimation of Chlorine

Chlorine was estimated gravimetrically by standard procedure12

as silver

chloride.

Estimation of Nitrogen

Nitrogen was estimated by standard Kjeldahl’s method.12,13

Estimation of Sulphur

Sulphur was estimated gravimetrically12,14

as barium sulphate.

172

Estimation of ruthenium, rhodium and iridium

These metal were estimated gravimetrically15-17

by precipitating them as

hydroxides and reducing to respective metal oxide.

3.7. Physical measurements

Infrared spectral studies

The infrared spectral studies of ligands and their respective metal complexes

were compared in order to determine the coordination mode of the ligands. Infrared

spectrum of synthesized ligand and complexes in the range 4000-200cm-1

were

recorded in KBr pellets in a Perkin Elmer Spectrum RXI on Schimadzu-8201 PC, FTIR

spectrophotometer.

Electronic spectral studies

The electronic spectral studies of the complexes were recorded in CHCl3 or

dimethyl formamide using Perkin Elmer Lambda 15 UV/ Vis spectrometer.

Absorption spectra show particular wave length of light absorbed i.e. the particular

amount of energy required to promote an electron from lower energy level to higher

energy level. The interpretation of spectra provides the most useful information

regarding and understanding of the energy levels present in the molecules.

Proton Magnetic Resonance spectral studies

1H-NMR spectra of the synthesized ligand and complexes were recorded in

deuterated (CDCl3) or dimethylsulphoxide (DMSO, d6) by using TMS

(Tetramethylsilane) as internal standard with a Bruker DRX-400 MHz Bruker,

spectrophotometer at SAIF, Central Drug Research Institute, Lucknow.

173

Electrical conductance

Electrical conductance measurements of various compounds were recorded by

Systronic Conductivity Meter (Model Number 306) in dimethylformamide at room

temperature.

Magnetic Susceptibility

Magnetic susceptibility measurements18-20

were recorded at room temperature

by Gouy’s balance by using mercuric tetrathiocyanato cobaltate(II) Hg[Co(SCN)4] (χg

= 16.44×10-6

CGS units at 20˚C), Cobalt mercury tetrathiocyanate as a calibrant. The

suspensions were kept in a closed glass chamber. Tube constants were checked from

time to time to ensure the satisfactory working at apparatus. Dimagnetic correction

was made using pascal’s constant.

Magnetic susceptibility (χg) has been calculated using formula:

(χg) = 1/W (αv + βƒ)

Where,

W = weight of substance in grams

α = volume of susceptibility of air (-0.029 × 10-6

c.g.s. unit at 20˚C)

β = tube constant

ƒ = pull on specimen (including the pull on empty tube)

For the purpose of diamagnetic correction, it is convenient to deal in terms

of susceptibility per mole of compound, i.e. molar susceptibility (χm), which was

obtained by multiplying the χg with molecular weight of the substance.

χm = χg × molecular weight

Magnetic corrections were applied using Pascal’s constant. The effective

magnetic moment value

(µeff) = 2.83 (χmcorr

× T)1/2

174

Where,

T = absolute temperature

χmcorr

= molar susceptibility obtained after employing the diamagnetic corrections.

The magnetic moment is usually expressed in a unit called Bohr Magnetons

abbreviated as B.M.

FAB MASS Spectral studies

FAB mass spectra were recorded on a JEOL SX-102/ DA-6000 mass

spectrometer/ Data System using argon/ Xenon (6KV, 10MA) as the FAB gas. The

accelerating voltage was 10KV and the spectra were recorded at room temperature,

m-nitrobenzyl alcohol (NBA) was used as the matrix.

Thermal studies

Thermogravimetric analysis is an effective tool to study the nature of

decomposition of the metal complexes. The thermal stability of the synthesized

complexes can be determined using this method. Thermogravimetric analysis was

carried out on Du Pont TGA 2950 analyzer with a heating rate of 10˚C per minute.

Melting point determination

The melting point of the synthesized ligand and their complexes was

determined by open fine capillary method using electrical ambassador melting point

apparatus.

175

3.8. References

1. A. I. Vogel, “A Text Book of Practical Organic Chemistry”, 4th

Edn.

Longmans, London, 1978.

2. A. M. A. Hassaan, Egypt J. Pharm. Sci., 35, 165, 1994.

3. R. C. Maurya and S. Rajput, J. Mol. Struct., 794, 24, 2006.

4. P. Selvam, M. Chandramohan, E. De Clercq, M. Witvrouw and C.

Pannecouque, Eur. J. Pharma. Sci., 14, 313, 2001

5. A. J. Abdulghani and N. M. Abbas, Bioinorg. Chem. Appl., ID 706262, 2011.

6. T. D. Thangadurai and K. Natarajan, Trans. Met. Chem., 27, 485, 2002.

7. R. S. Seni and K. M. Saha, J. Inorg. Chem., 42, 231, 2010.

8. Efimovsky and P. Rumpt, Bull. Soc. Chim., Fr., 648, 1954.

9. G. M. Shashidhara and T. R. Goudar, J. Indian Chem. Soc., 78, 360, 2001.

10. N. Tripathi, Shalini and V. K. Sharma, Rev. Roum. Chim., 56, 189, 2011.

11. E. L. Chang, C. Simmers and D. A. Knight, Pharmaceuticals, 3, 1711, 2010.

12. A. I. Vogel, “Elementary Practical Organic Chemistry” Part 3: Quantitative

Organic Analysis, Longmans, London, 1975.

13. W. L. Jolly, “The synthesis and characterization of Inorganic compounds”,

Prentice Hall Inc., 1970.

14. J. W. Zubrick, “The Organic Chem. Lab Survival Manual”, John Wiley and

sons, 1988.

15. L. Erdey, “Gravimetric Analysis” Part 2, Pergamon Press, 1965.

16. C. L. Wilson and D. W. Wilson, “Comprehensive Analytical Chemistry”,

Elseviers, 628, 1962.

17. F. E. Beamish, “The Analytical Chemistry of the Noble Metals”, Pergamon

Press, 1966.

176

18. R. S. Drago, “Physical Methods for Chemists”, 2nd

Edn., Saunders College

Publishing, 1992.

19. R. L. Carlin “Magnetochemistry” Springer Verlag, New York, 1986.

20. R. L. Dutta and A. Syamal, “Elements of Magnetochemistry”, East-West

Press, 1993.

177

CHAPTER 4

Schiff bases play an important role in inorganic chemistry as they easily form

stable complexes with most transition metal ions. The development of the field of

bioinorganic chemistry has increased the interest in Schiff base complexes, since it

has been recognized that many of these complexes may serve as models for

biologically important species.1-11

The reaction is accompanied by the elimination of

one molecule of water may be expressed by following general reaction:

C7H4NOCHO + H2NC6H4O2SNHR → C7H4NOCH=NC6H4O2SNHR + H2O

Schiff bases have often been used as chelating ligands in the field of

coordination chemistry and their metal complexes are of great interest for many years.

Schiff base metal complexes have been widely studied because they have industrial,

anticancer and herbicidal applications.12,13

They serve as models for biologically

important species and find applications in biomimetic catalytic reactions. Isatin and its

derivatives have been extensively used as versatile reagents in organic synthesis: to

obtain heterocyclic compounds and as raw material for drugs.14-17

Although there is a

wealth of information concerning transition metal complexes with isatin Schiff

bases.18-21

In particular, the study of organic chelating agents containing nitrogen and

sulphur as the donor atoms and their metal complexes has become a subject of

intensive investigation. The investigators in the area of Schiff base ligands are

concentrating on their biological activity like potent inhibitors and variable bonding.

The pronounced biological activity of the metal complexes of Schiff bases derived

from sulpha drugs has led to considerable interest in their coordination chemistry. The

condensation products of sulpha drugs with aldehydes and ketones are biologically

active and also have good complexing ability.22-27

Isatin and its derivatives have been

178

extensively used as versatile reagents in organic synthesis, to obtain heterocyclic

compounds and as raw material for drugs. Some synthetic oxindole based compounds

have been developed as anticancer, anti-HIV or antimicrobial agents.28-35

Compounds

containing the sulphonamide group have long been used as drugs for diseases like

cancer, tuberculosis, diabetes, malaria and leprosy.36-37

In addition of this, they have

been screened for their medicinal properties because they possess some cytotoxic

effect. They also stabilize uncommon oxidation states; generate a different

coordination number in transition metal complexes in order to participate in various

redox reactions. The complexes with Schiff bases are very important due to their

application in medicine, particularly in the chemotherapy of cancer. Inorganic

chemistry has been enriched by the continuing development of coordinating chemistry

and the entry of a new thinking from organic perspective. In recent years great

expansion of research in the coordinating chemistry metal chelates involving

chelating Schiff base containing nitrogen, oxygen and sulphur donors. Metal

coordination complexes have wide diversity of applications including catalytic

industrial and biological.38-45

In this view present chapter reveals that a number of complexes with these

ligands have been reported for a variety of transition metals which have shown

interesting biological and magnetic properties.46-50

To extend the knowledge with

respect to coordination and biological properties of ruthenium(III) complexes of

ligands, we describe here the synthesis and characterisation of series of ruthenium

complexes with Schiff bases derived from various sulpha drugs i.e. sulphanilamide,

sulphamerazine, sulphaguanidine, sulphadiazine, sulphacetamide and sulphapyridine.

These ligands behave as monoanionic bidentate ligand coordinating to metal centre

through the deprotonated phenolic oxygen and azomethine nitrogen. The results of

179

preparation, spectroscopic investigations of the synthesized ligands and their chelates

are discussed in this article.

The condensation reaction of isatin with various sulpha drugs (1:1 ratio) in

ethanol gives rise to Schiff bases as shown below:

NH

O

N S

O

O

NHR

Where,

R Abbreviation

H IShAH

N

N CH3

IShMH

C

NH

NH2

IShGH

N

N

IShDH

C

O

CH3

IShAcH

N

IShPH

Fig. 1: Structure of the ligand

180

4.1. EXPERIMENTAL

The syntheses of ligands are described previously in chapter 3. Using the

present source of investigation complexes of ruthenium(III) have been synthesized.

(i) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphanilamide (IShAH) in 1:2 ratio.

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShAH (0.300 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 18-20 hours with constant stirring (pH 6-7). The colour of solution

changed from brownish black to purple. The coloured complex precipitated. The

volume of solution was reduced to 1/4th

of its volume and poured in ice cold water to

good yield precipitate. The black colour complex precipitated was obtained. The

product was filtered, washed with ethanol and dried in vacuum over fused CaCl2 at

room temperature. Yield was 47%.

(ii) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphamerazine (IShMH) in 1:2 ratio

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShMH (0.345 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 20-23 hours with constant stirring (pH 6-7). The colour of solution

changes becomes brownish. The coloured complex precipitated. The volume of

181

solution was reduced to 1/4th

of its volume and poured in ice cold water to good yield

precipitate. The brown colour complex precipitated was obtained. The product was

filtered, washed with ethanol and dried in vacuum over fused CaCl2 at room

temperature. Yield was 51%.

(iii) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphaguanidine (IShGH) in 1:2 ratio

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShGH (0.345 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 20-24 hours with constant stirring (pH 6-7). The colour of solution

changed from brownish to green. The coloured complex precipitated. The volume of

solution was reduced to 1/4th

of its volume and poured in ice cold water to good yield

precipitate. The greenish colour complex precipitated was obtained. The product was

filtered, washed with ethanol and dried in vacuum over fused CaCl2 at room

temperature. Yield was 64%.

(iv) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphadiazine (IShDH) in 1:2 ratio

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShDH (0.380 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 20-25 hours with constant stirring (pH 6-7). The colour of solution

changed from brown to chocolate brown. The coloured complex precipitated. The

182

volume of solution was reduced to 1/4th

of its volume and poured in ice cold water to

good yield precipitate. The brown colour complex precipitated was obtained. The

product was filtered, washed with ethanol and dried in vacuum over fused CaCl2 at

room temperature. Yield was 60%.

(v) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphacetamide (IShAcH) in 1:2 ratio

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShAcH (0.345 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 20-24 hours with constant stirring (pH 6-7). The colour of solution

changed from brownish black to purple. The coloured complex precipitated. The

volume of solution was reduced to 1/4th

of its volume and poured in ice cold water to

good yield precipitate. The black colour complex precipitated was obtained. The

product was filtered, washed with ethanol and dried in vacuum over fused CaCl2 at

room temperature. Yield was 62%.

(vi) Synthesis of ruthenium(III) complex with Schiff base derived from isatin and

sulphapyridine (IShPH) in 1:2 ratio

The general procedure with stoichiometric amount of ethanolic solution of

ruthenium(III) chloride trihydrate (0.130 g, 0.01 mol) was suspended in Schiff base

ligand IShPH (0.380 g, 0.01 mol) was added to an ethanol (20 ml) taken in separate

round bottom flask and heated till clear solution obtained. The reaction mixture is

refluxed for 18-20 hours with constant stirring (pH 6-7). The colour of solution

changed from violet to grey. The coloured complex precipitated. The volume of

183

solution was reduced to 1/4th

of its volume and poured in ice cold water to good yield

precipitate. The grey colour complex precipitated was obtained. The product was

filtered, washed with ethanol and dried in vacuum over fused CaCl2 at room

temperature. Yield was 48%.

All the reactions are summarized in Table 4.II and analytical data are given

in Table 4.II.

184

Table: 4.I. Reactions of ruthenium (III) chloride with Schiff bases derived from isatin and various sulpha drugs.

Reactants Molar ratio Stirring/Refluxing

time (hrs)

Product Colour Decomp.

Temp.

Yield (%)

RuCl3∙3H2O + IShAH 1:2 18 [Ru(IShA)2(H2O)2]Cl Dark black 260 47

RuCl3∙3H2O + IShMH 1:2 20 [Ru(IShM)2(H2O)2]Cl Chocolate brown 262 51

RuCl3∙3H2O + IShGH 1:2 20 [Ru(IShG)2(H2O)2]Cl Greenish black 260 64

RuCl3∙3H2O + IShDH 1:2 20 [Ru(IShD)2(H2O)2]Cl Dark grey 250 60

RuCl3∙3H2O + IShAcH 1:2 21 [Ru(IShAC)2(H2O)2]Cl Brown 253 62

RuCl3∙3H2O + IShPH 1:2 19 [Ru(IShP)2(H2O)2]Cl Violet 250 48

185

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

186

Table: 4.II. Analytical data of ruthenium(III) complexes with Schiff bases derived from isatin and various sulpha drugs.

Complexes M.Wt.

Found

(Calcd.)

Analysis found (calcd.)%

C H N S Cl Ru

[Ru(IShA)2(H2O)2]Cl 773

(773.1)

42.08

(43.49)

3.10

(3.12)

10.20

(10.86)

7.26

(8.29)

4.15

(4.58)

12.72

(13.07)

[Ru(IShM)2(H2O)2]Cl 957

(957.4)

46.80

(47.67)

3.25

(3.36)

14.20

(14.62)

5.80

(6.69)

3.55

(3.70)

9.66

(10.55)

[Ru(IShG)2(H2O)2]Cl 857

(857.2)

41.82

(42.03)

3.20

(3.29)

15.88

(16.33)

6.60

(7.48)

3.95

(4.13)

10.72

(11.78)

[Ru(IShD)2(H2O)2]Cl 929

(929.3)

45.25

(46.52)

2.98

(3.03)

14.88

(15.07)

6.55

(6.90)

3.75

(3.87)

10.26

(10.87)

[Ru(IShAc)2(H2O)2]Cl

857

(857.2)

43.90

(44.83)

3.15

(3.29)

9.26

(9.80)

6.70

(7.48)

3.82

(4.13)

10.12

(11.78)

[Ru(IShP)2(H2O)2]Cl 927

(927.3)

48.90

(49.21)

2.95

(3.26)

11.78

(12.08)

6.42

(6.91)

3.46

(3.82)

10.26

(10.89)

187

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

188

4.2. RESULTS AND DISCUSSION

The condensation of sulpha drugs viz. sulphanilamide, sulphamerazine,

sulphaguanidine, sulphadiazine, sulphacetamide and sulphapyridine with isatin in

(molar ratio 1:1) ethanol containing a few drops of concentrate hydrochloric acid

gives rise to Schiff base (LH) as shown in Fig. 2

NH

O

N S

O

O

NHR

NH

OH

N S

O

O

NHR

NH

O

O

S

O

O

NHRH2N+

-H2O Ethanol

R = H,

N

N CH3,

C

NH

NH2 , N

N

,

C

O

CH3, N

Fig. 2: Scheme of the ligand

189

A systematic study of reactions of the ruthenium(III) chloride with Schiff

bases (LH) derived from isatin and various sulpha drugs (molar ratio 1:2) in ethanol

may be represented by the following equation.

RuCl3 + 2LH → [Ru(L)2(H2O)2]Cl + 2HCl

Where; LH = IShAH, IShMH, IShGH, IShDH, IShAcH and IShPH.

The analytical, physical and spectral data are comparable with the suggested

structures. All the complexes are coloured and powdered form and soluble in THF,

DMF and DMSO. The Schiff base were expected to behave as a bidentate with

oxygen and nitrogen as donor atoms or coordination sites. All the ruthenium(III)

complexes being d5

(low spin), S = 1/2 behave as paramagnetic. The obtained

microcrystalline complexes were found to be stable in air and with colour variation

from brown to black. The melting point of all the complexes was determined by open

capillary method. The molar conductance of the complexes in DMF indicates the 1:1

electrolytic behaviour.51

Thus, the complexes may be formulated as

[Ru(L)2(H2O)2]Cl. The main techniques by which attempts have been made to

through light on the stereochemistry of ruthenium(III) complexes synthesized during

the present course of investigations are UV-visible, infrared, proton magnetic

resonance and FAB mass spectral studies along with magnetic measurements and

thermal studies. Comparing the IR spectra of the complexes with the spectra of the

free ligands elucidated the mode of binding of the Schiff bases to the metal ions. The

presence of chloride ion in outer sphere was tested both qualitatively and

quantitatively and found very positive.

MAGNETIC MOMENTS

Magnetic moments are often used in conjunction with electronic spectra to

gain information about the oxidation number and stereochemistry of the central metal

190

ion in coordination complexes. At the room temperature the magnetic moment of the

ruthenium complexes lie between 1.80-2.10 B.M.52,53

That is very close to the spin

only value, suggesting the octahedral geometry around ruthenium ion. The values thus

obtained correspond to the presence of one unpaired d electron leading to +3

oxidation state for ruthenium.54,55

ELECTRONIC SPECTRAL STUDIES

In a d5 system ruthenium(III) which is a relatively strong oxidizing agent,

charge transfer bands are prominent in the low-energy region and obscure the weaker

bands due to the d–d transition. The electronic spectrum of the low spin

ruthenium(III) complexes recorded in DMSO displays three spin allowed transitions.

The ruthenium(III) is a d5

system with ground state 2

T2g

and first excited doublet

levels in the order of increasing energy are 2

A2g

and 2

A1g

, which arises from t2g

4 eg1

configuration.56

In most of UV-vis spectra of ruthenium(III) complexes only charge

transfer bands occur. These bands are characteristic of an octahedral geometry.

Spectra of all ruthenium(III) complexes displayed bands at 13908-15356 cm-1

and

17241-20202 cm-1

assigned to 2T2g →

4T1g and

2T2g→

4T2g. The two lowest energy

absorptions corresponding to 2T2g→

4T1g and

2T2g→

4T2g were frequently observed as

shoulder to charge transfer bands. The bands in the region 26525-31250 cm-1

has

been assigned to 2T2g→

2A2g transition in ruthenium complexes.

57,58

The electronic spectral bands with assignments for ruthenium(III) complexes

are summarized in Table 4.III.

191

Table: 4.III. Magnetic moment and electronic spectral data of ruthenium(III) complexes with Schiff bases derived from isatin and

various sulpha drugs.

Complexes λmax (cm-1

) Assignments µeff (B.M.)

[Ru(IShA)2(H2O)2]Cl 13908

17241

26525

2T2g →

4T1g

2T2g→

4T2g

2T2g→

4A2g

2.10

[Ru(IShM)2(H2O)2]Cl 15037

20120

30487

-do- 1.80

[Ru(IShG)2(H2O)2]Cl 15356

17391

30461

-do- 1.94

[Ru(IShD)2(H2O)2]Cl 14285

17857

31250

-do- 1.92

[Ru(IShAc)2(H2O)2]Cl 13966

20202

27777

-do- 1.90

[Ru(IShP)2(H2O)2]Cl 14285

17857

31250

-do- 2.10

192

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

193

INFRARED SPECTRAL STUDIES

The infrared Spectra of the Schiff base ligands were compared with that of

metal complexes to obtain the information about the binding mode of ligands in the

complexes. The ligands can act either in keto or in enolic form, depending upon the

conditions (e.g. pH of the medium, oxidation state of the metal ion). All

physicochemical properties of the complexes support bidentate chelation of the

ligands by the nitrogen and by oxygen. This fact was further supported by the bands

including azomethine nitrogen ν(C=N) at 1615–1694 cm-1

in ligands and the lowering

of this band by 20-35 cm-1

in complexes results in chelation of the nitrogen to metal

ion.59

In the spectra of the ligands the presence of bands at 3040-3200 cm-1

and 1672-

1680 cm-1

assigned to ν(N-H) and ν(C=O) vibrations of isatin moiety respectively.60

These bands disappear in ruthenium(III) complexes, which may be due to enolization

of keto group. The spectra of free Schiff bases show a medium band at ca. 3140 cm-1

due to ν(N-H), which persists almost at the same position in the complexes indicating

the non-involvement of this group in bond formation. The band at ca. 1370 and ca.

1150 cm-1

are assigned to νas(SO2) and νs(SO2), respectively. Further no shift in the

absorption bands of SO2 has been observed thereby indicating the nonparticipation of

sulphonamide oxygen in the bonding.61

The band in the range 1615-1694 and 1480-

1500 cm-1

in the spectra of ligands may be assigned to ν(C=N) and ν(C=C) (phenyl)

vibrations, respectively.62

The coordination modes are further confirmed by the

presence of bands in the range 450-490 cm-1

and 440-460 cm-1

in complexes spectra

assigned to ν(Ru-N) and ν(Ru-O) vibrations, respectively.63

In addition, all

complexes show broad band at 3400 cm-1

due to ν(OH) of coordinated water

molecules.64

Thus, The infrared spectra reveal that the Schiff base ligands behave as

194

monobasic, bidentate ligands coordinating through one azomethine nitrogen and one

enolic oxygen through deprotonation.65

The infrared spectral bands of the ligands and their corresponding complexes

are summarized in Table 4.IV.

195

Table: 4.IV. Infrared spectral band (cm-1

) of the Schiff bases derived from isatin and various sulpha drugs and their ruthenium(III)

complexes.

Compound ν(NH) ν(C=N) ν (C-O) ν(SO2) ν(Ru-N) ν(Ru-O)

IShAH 3160, 3050 1655 1293 1376, 1150 - -

IShMH 3150, 3125 1694 1292 1372, 1148 - -

IShGH 3200, 3065 1622 1280 1370, 1140 - -

IShDH 3140, 3100 1680 1294 1371, 1132 - -

IShAcH 3130, 3060 1615 1290 1372, 1138 - -

IShPH 3139, 3040 1615 1293 1371, 1149 - -

[Ru(IShA)2(H2O)2]Cl 3120 1600 1375 1372, 1150 485 445

[Ru(IShM)2(H2O)2]Cl 3135 1589 1378 1370, 1147 482 460

[Ru(IShG)2(H2O)2]Cl 3145 1600 1379 1371, 1149 490 455

[Ru(IShD)2(H2O)2]Cl 3110 1588 1376 1372, 1152 470 450

[Ru(IShAc)2(H2O)2]Cl 3080 1595 1380 1370, 1138 495 445

[Ru(IShP)2( H2O)2]Cl 3090 1590 1372 1371, 1139 475 455

196

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

197

PROTON MAGNETIC RESONANCE SPECTRAL STUDIES

The proton magnetic resonance spectra of the ligands were recorded in

deuterated dimethylsulphoxide. The ligand has protons in different chemical

environments. The spectra of ligands show the expected signals due –NH, aromatic

protons and –CH3. The following conclusions can be derived by spectra of the

ligands. The signals of ligands observed for N-H protons appeared at δ8.06-8.69 ppm.

The chemical shift of certain aromatic protons appeared as broad multiplets in the

range of δ6.96-7.85 ppm, but in ligands which is highly diagnostic for their

environment. In IShMH and IShDH the methyl protons appear as singlet in the region

δ1.8-2.2 ppm. Thus, compounds prepared got the kind of structural support by proton

magnetic resonance spectral data.

The data regarding proton magnetic resonance spectra are given in their

corresponding Table 4.V.

198

Table: 4.V. Proton magnetic resonance spectral data (δ, ppm) of the Schiff bases derived from isatin and various sulpha drugs.

Compounds δ(N-H) δ(CH3) δ(Ar-H)

IShAH 8.6 (s) - 6.96 (m)

IShMH 8.0 (s) 2.2 (s) 7.88 (m)

IShGH 8.5 (s) - 7.26 (m)

IShDH 8.6 (s) 1.8 (s) 7.05 (m)

IShAcH 8.2 (s) - 7.27 (m)

IShPH 8.0 (s) - 7.85 (m)

Where,

IShAH = Schiff base derived from isatin and sulphanilamide

IShMH = Schiff base derived from isatin and sulphamerazine

IShGH = Schiff base derived from isatin and sulphaguanidine

IShDH = Schiff base derived from isatin and sulphadiazine

IShAcH = Schiff base derived from isatin and sulphacetamide

IShPH = Schiff base derived from isatin and sulphapyridine

199

FAB MASS SPECTRAL STUDIES

Mass spectroscopy mainly applied in analyses of biomolecules has been

increasingly used as a powerful structure characterization technique in the

coordination chemistry. The mass spectra of the ligands and complexes are compared.

Their fragmentation revealed the exact composition of the compounds formed. Mass

spectra of the ligands namely IShAH, IShMH, IShGH, IShDH, IShAcH and IShPH

show molecular peak at m/z = 301, 393, 343, 379, 343 and 378 which corresponds to

their molecular weight. The molecular ion peaks for the complexes of ruthenium(III)

are observed at m/z = 773, 957, 857, 929, 857 and 927 they are in good agreement

with their molecular weights. Therefore, above fragmentation pattern complemented

the exact composition of the various compounds and described the stoichiometry in

which complexes has been formed.

THERMAL STUDIES

Thermal analysis is a branch of material science where the properties of

materials are studies as they change with temperature. Thermal studies of the Schiff

base complexes were carried out in order to get (i) information about thermal stability

of new complexes, (ii) to decide whether the water molecule is inside or outside of the

coordination sphere of central metal ion and (iii) to propose a general scheme for

thermal decomposition of these chelates. The numbers of chelates rings as well as the

type of chelates rings around the metal ion play an important role in thermal stability

and decomposition of the complexes. Thermogravimetry data reveals that the

ruthenium(III) complexes decompose in two steps. The presence of water molecules

suggested from infrared spectra is confirmed by TG and DTG data. Ruthenium(III)

complexes lose their weight and become stable in the temperature range 260-320˚C

200

corresponding to one uncoordinated chloride and two coordinated water molecules.

The organic moiety decomposed further with the increasing temperature. Although

decomposed weight loss, the complete decomposition of the ligand occurred at

~620˚C in all the complexes. At the end of the final step, i.e., 680-720˚C, stable

metallic oxides Ru2O3 were formed. Thus, the composition of the intermediate

complexes may be fortuitous although the weight losses indicated the above

stoichiometries.

On the basis of above spectral studies the following structures are suggested

for the complexes.

N O

N

SO O

NHR

Ru

NO

N

S OO

NHR

OH2

OH2

Cl

Fig. 3: The proposed structure of complex

201

CONCLUSION

The ruthenium(III) complexes of the type [Ru(L)2(H2O)2]Cl with Schiff bases

derived from isatin and various sulpha drugs have been synthesized and characterized

on the basis of analysis, electrical conductance, magnetic moment and spectral data.

The ligands act as monobasic bidentate coordinating through the azomethine nitrogen

and enol oxygen atoms. The six coordinated structure of complexes have been

proposed. All the complexes are 1:1 electrolytic behaviour.

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206

CHAPTER 5

Multidentate ligands are extensively used for the preparation of metal complexes

with interesting properties. Among these ligands, Schiff bases containing nitrogen and

phenolic oxygen donor atoms are of considerable interest due to their potential

application in catalysis, medicine and material science.1-4

Recent years have witnessed

discernible growth in interest in Schiff bases and their metal complexes due to their

facile synthesis, wide application,5-14

diversity and structural variability.15-21

Schiff

bases are an important class of ligands based on their potential use as ligands at a metal

centre, their complexing ability containing different donor atom are widely reported.22-28

Sulphonamides were the first drugs found to act selectively and could be used

systematically as preventive and therapeutic agents against various diseases.29

Sulphur

ligands are widespread among co-ordination compounds and are important components

of biological transition metal complexes.30,31

Metal components with sulphur containing

unsaturated ligands are also of a great interest in inorganic and organometallic

chemistry, especially due to their potential with novel electrical and magnetic

properties. Schiff bases continue to occupy an important position as ligand in metal

coordination chemistry,32,33

even almost a century since their discovery. The study of

various types of heteroaromatic containing Schiff bases linked to metal complexes has

received a great deal of attention during past decades.34,35

Chelating ligands containing

N and O donor atoms show broad biological activity and are of special interest because

of variety of ways in which they are bonded to metal ions.36,37

Aromatic

hydroxyaldehydes form stable complexes and the presence of a phenolic hydroxyl

group at their o-position imparts an additional donor site in the molecule making it

207

bidentate. Such a molecule coordinates with the metal ion through the carbonyl oxygen

and the deprotonated hydroxyl group. The chelating properties of Schiff bases derived

from hydroxyaldehydes and ketones are well established.38-40

It was, therefore, considered of interest to synthesize ruthenium(III) derivatives

of Schiff bases derived by condensation of o-vanillin, salicylaldehyde and 2-hydroxy-1-

naphthaldehyde with sulphanilamide and sulphamerazine. The structure of the ligands

are depicted below:

S N R"

H

NC

R'

H

O

O

R’ R” Abbreviation

OH

OCH3

H oVSaH

OH

OCH3 N

N CH3

oVSmrzH

OH

H SdSaH

OH

N

N CH3

SdSmrzH

OH

H 2hNSaH

OH

N

N CH3

2hNSmrzH

Fig. 1: Structure of the ligands

208

5.1. EXPERIMENTAL

The synthesis of the Schiff base ligands are given in chapter 3.

RUTHENIUM(III) COMPLEXES WITH SCHIFF BASE DERIVED FROM

SULPHA DRUGS AND VARIOUS ALDEHYDES

(i) Synthesis of ruthenium(III) complex with Schiff base derived from o-Vanillin

and sulphanilamide (oVSaH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (3.063 g, 0.01 mol) of hot ethanolic solution of o-Vanillin

sulphanilamide (oVSaH). The resulting mixture was then refluxed on a heating mantle

with constant stirring at 80oC for around 6-7 h. The color of the solution changed from

black to dark brown. On cooling a dark brown solid precipitated out which was suction

filtered, washed with ethanol and finally with diethyl ether and dried over anhydrous

calcium chloride.

(ii) Synthesis of ruthenium(III) complex with Schiff base derived from o-Vanillin

and sulphamerazine (oVSmrzH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (2.763 g, 0.01 mol) of hot ethanolic solution of Salicylaldehyde

sulphamerazine (oVSmrzH). The resulting mixture was then refluxed on a heating

mantle with constant stirring at 80oC for around 8-9 h. The color of the solution

changed from black to olive black. On cooling a crystalline dirty brown solid

209

precipitated out which was suction filtered, washed with ethanol and finally with diethyl

ether and dried over anhydrous calcium chloride.

(iii) Synthesis of ruthenium(III) complex with Schiff base derived from

Salicylaldehyde and sulphanilamide (SdSaH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (2.763 g, 0.01 mol) of hot ethanolic solution of Salicylaldehyde

sulphanilamide (SdSaH). The resulting mixture was then refluxed on a heating mantle

with constant stirring at 80oC for around 8-9 h. The color of the solution changed from

black to olive black. On cooling a crystalline dirty brown solid precipitated out which

was suction filtered, washed with ethanol and finally with diethyl ether and dried over

anhydrous calcium chloride.

(iv) Synthesis of ruthenium(III) complex with Schiff base derived from

Salicylaldehyde and sulphamerazine (SdSmrzH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (3.684 g, 0.01 mol) of hot ethanolic solution of Salicylaldehyde

sulphamerazine (SdSmrzH). The resulting mixture was then refluxed on a heating

mantle with constant stirring at 80oC for around 8-9 h. The color of the solution

changed from black to brown. On cooling a crystalline black solid precipitated out

which was suction filtered, washed with ethanol and finally with diethyl ether and dried

over anhydrous calcium chloride.

210

(v) Synthesis of ruthenium(III) complex with Schiff base derived from 2-hydroxy-

1-naphthaldehyde and sulphanilamide (2hNSaH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (3.264 g, 0.01 mol) of hot ethanolic solution of 2-hydroxy-1-

naphthaldehyde sulphanilamide (2hNSaH). The resulting mixture was then refluxed on

a heating mantle with constant stirring at 80oC for around 9-10 h. The color of the

solution changed from mud black color to brown. On cooling a tan brown solid

precipitated out which was suction filtered, washed with ethanol and finally with diethyl

ether and dried over anhydrous calcium chloride.

(vi) Synthesis of ruthenium(III) complex with Schiff base derived from 2-hydroxy-

1-naphthaldehyde and sulphamerazine (2hNSmrzH) in 1:2 ratio.

The complex was prepared by reacting 1:2 metal to ligand molar ratios. A

magnetically stirred, prepared ethanolic solution (30 ml) of RuCl3·3H2O (1.30 g, 0.005

mol) was added to (3.855 g, 0.01 mol) of hot ethanolic solution of 2-hydroxy-1-

naphthaldehyde sulphamerazine (2hNSmrzH), the resulting mixture was then refluxed

on a heating mantle with constant stirring at 80o

C for around 9-10 h. The color of the

solution changed from black to dark brown. On cooling a blackish brown solid

precipitated out which was suction filtered, washed with ethanol and finally with diethyl

ether and dried over anhydrous calcium chloride.

All the reactions are summarized in their corresponding Table 5.I and analytical

data are given in Table 5.II.

211

Table: 5.I. Reactions of ruthenium(III) chloride with Schiff bases derived from sulpha drugs and various aldehydes.

Reactants Molar ratio Stirring/Refluxing

time (hrs)

Product Colour Decomp.

Temp.

Yield (%)

RuCl3∙3H2O + oVSaH 1:2 7 [Ru(oVSa)2(H2O)Cl] Dark brown 255 65

RuCl3∙3H2O + oVSmrzH 1:2 8 [Ru(oVSmrz)2(H2O)Cl] Brown 260 58

RuCl3∙3H2O + SdSaH 1:2 9 [Ru(SdSa)2(H2O)Cl] Dirty brown 262 53

RuCl3∙3H2O + SdSmrzH 1:2 8 [Ru(SdSmrz)2(H2O)Cl] Black 268 59

RuCl3∙3H2O + 2hNSaH 1:2 10 [Ru(2hNSa)2(H2O)Cl] Tan brown 270 60

RuCl3∙3H2O + 2hNSmrzH 1:2 10 [Ru(2hNSmrz)2(H2O)Cl] Blackish

brown

265 57

212

Where,

oVSaH = Schiff base derived from o-Vanillin and sulphanilamide

oVSmrzH = Schiff base derived from o-Vanillin and sulphamerazine

SdSaH = Schiff base derived from Salicylaldehyde and sulphanilamide

SdSmrzH = Schiff base derived from Salicylaldehyde and sulphamerazine

2hNSaH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphanilamide

2hNSmrzH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphamerazine

213

Table: 5.II. Analytical data of ruthenium(III) complexes with Schiff bases derived from sulphadrugs and various aldehyde.

Complexes M.Wt.

Found

(Calcd.)

Analysis found (calcd.)%

C H N S Cl Ru

[Ru(oVSa)2(H2O)Cl] 768

(767.2)

42.32

(43.83)

3.85

(3.94)

7.15

(7.30)

8.15

(8.35)

4.42

(4.62)

12.70

(13.17)

[Ru(oVSmrz)2(H2O)Cl] 952

(951.4)

45.08

(47.97)

3.90

(4.02)

10.20

(11.77)

6.26

(6.74)

3.15

(3.72)

10.42

(10.62)

[Ru(SdSa)2(H2O)Cl] 708

(707.2)

43.80

(44.16)

3.55

(3.70)

7.20

(7.92)

8.80

(9.06)

4.55

(5.01)

13.66

(14.29)

[Ru(SdSmrz)2(H2O)Cl] 892

(891.4)

46.82

(48.50)

3.60

(3.84)

11.88

(12.57)

6.60

(7.19)

3.95

(3.97)

10.72

(11.33)

[Ru(2hNSa)2(H2O)Cl] 808

(807.3)

48.25

(50.58)

3.38

(3.74)

6.88

(6.94)

7.55

(7.94)

3.85

(4.39)

11.26

(12.51)

[Ru(2hNSmrz)2(H2O)Cl] 988

(987.5)

52.90

(53.41)

3.45

(3.66)

10.26

(11.32)

6.40

(6.48)

3.42

(3.58)

10.12

(10.25)

214

Where,

oVSaH = Schiff base derived from o-Vanillin and sulphanilamide

oVSmrzH = Schiff base derived from o-Vanillin and sulphamerazine

SdSaH = Schiff base derived from Salicylaldehyde and sulphanilamide

SdSmrzH = Schiff base derived from Salicylaldehyde and sulphamerazine

2hNSaH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphanilamide

2hNSmrzH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphamerazine

.

215

5.2. RESULTS AND DISCUSSION

Systematic study of reactions of ruthenium(III) chloride with Schiff base ligand

1:2 ratio synthesized in combination of hydroxyl aromatic aldehydes and sulpha drugs

(sulphanilamide or sulphamerazine) in 1:1 molar ratio in ethanol. The complexes of

type [Ru(L)2(H2O)Cl] are obtained according to the following reaction.

RuCl3·3H2O + 2LH → [Ru(L)2(H2O)Cl] + 2HCl

LH = oVSaH, oVSmrzH, SdSaH, SdSmrzH, 2hNSaH, 2hNSmrzH

The analytical and physical data of the ligands and the complexes are in

agreement with their molecular formulae. All the complexes are found to be stable in air

and non-hygroscopic microcrystalline salts. Complexes exhibit good solubility in DMF,

DMSO, THF and poor solubility in diethyl ether, acetone and water. Complexes are

sparingly soluble in methanol and ethanol. All complexes were obtained in good yield

and are stable in phase. The very low conductance values in DMF (10-3

M) solution

indicate the non-electrolytic nature of the complexes. Ruthenium was estimated by

standard gravimetric method.41-43

MAGNETIC MOMENT

The important of µeff to chemist lies in the fact that for many compounds it can

be calculated theoretically from knowledge of the structure and bonding. Magnetic

susceptibility measurements of the complexes were performed at room temperature lie

in the range 1.82- 1.96 B.M., which expected to be lower than the predicted value of

2.10 B. M. The spin-only values were calculated using the equations µRu = 2[SRu(SRu +

1)]1/2

for complexes are markedly equal to/ or higher than spin-only value for one

unpaired electron for low spin t2g5

ruthenium(III) in an octahedral environment.

216

Therefore, these data indicate that ruthenium(III) complexes metal are in low-spin

states.44,45

ELECTRONIC SPECTRAL STUDIES

The low spin ruthenium(III) is a d5

system with ground state 2

T2g

and first

excited doublet levels in the order of increasing energy are 2

A2g

and 2

T1g

, which is arises

from t4

2geg

1 configuration. In most of UV-spectra of ruthenium(III) complexes only

charge transfer bands occur. These bands are characteristic of an octahedral geometry.

Spectra of all ruthenium(III) complexes displayed bands at 13550-14100 cm-1

(ν1) and

17340-18230 cm-1

(ν2) assigned to 2T2g →

4T1g and

2T2g→

4T2g. The two lowest energy

absorptions corresponding to 2T2g→

4T1g and

2T2g→

4T2g were frequently observed as

shoulders to charge transfer bands. The bands in the region 23660-23860 cm-1

(ν3) has

been assigned to 2T2g→

2A2g transition in ruthenium complexes.

46,47

The electronic spectra data are summarized in Table 5.III.

217

Table: 5.III. Magnetic moment and electronic spectral data of ruthenium(III) complexes with Schiff bases derived from sulpha drugs and

various aldehydes.

Complexes λmax (cm-1

) Assignments µeff (B.M.)

[Ru(oVSa)2(H2O)Cl] 13600

17340

23800

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.82

[Ru(oVSmrz)2(H2O)Cl] 13800

17360

23660

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.84

[Ru(SdSa)2(H2O)Cl] 14060

17660

23800

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.94

[Ru(SdSmrz)2(H2O)Cl] 13720

17410

23860

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.96

[Ru(2hNSa)2(H2O)Cl] 14100

18200

23680

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.88

218

[Ru(2hNSmrz)2(H2O)Cl] 13550

18230

23600

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g

1.92

Where,

oVSaH = Schiff base derived from o-Vanillin and sulphanilamide

oVSmrzH = Schiff base derived from o-Vanillin and sulphamerazine

SdSaH = Schiff base derived from Salicylaldehyde and sulphanilamide

SdSmrzH = Schiff base derived from Salicylaldehyde and sulphamerazine

2hNSaH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphanilamide

2hNSmrzH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphamerazine

219

INFRARED SPECTRAL STUDIES

The infrared spectra of the complexes are compared with those of the free ligand

in order to determine the coordination sites that may involve in chelation. In the present

investigation four possible donor sites (i) Phenolic oxygen, (ii) Azomethine nitrogen,

(iii) Sulphonamide nitrogen, (iv) Sulphonamide oxygen and (v) Ring nitrogen.

All the ligands display a strong and sharp band in the region 1615-1635 cm-1

which is due to ν(C=N) azomethine band. This band shifts to lower frequency by 10-25

cm-1

in the spectra after complexation, indicating the coordination of azomethine

nitrogen to metal ion.48,49

In the spectra of ligands, exhibit two broad peaks in the region

3040-3400 cm-1

due to the hydrogen bonded OH and NH.50

In the spectra of complexes,

the band due to OH gets shifted to the higher wave number region showing the

coordination of the ligand through the phenolic oxygen after deprotonation.51

However,

the νΝH band remains approximately at the same position, which clearly indicates the

non involvement of NH in complexation. This is further substantiated by the appearance

of ν(C-O) phenolic at lower frequencies (compared to 1355-1370 cm-1

in the ligands) in

the range 1340-1350 cm-1

, after complexation. The coordination of azomethine nitrogen

and phenolic oxygen is further supported by the appearance of bands at 480-500, 440-

460 cm-1

and 355-380 cm-1

due to ν(Ru-N), ν(Ru-O) and ν(Ru-Cl), respectively in all

complexes.52

A broad band in the region 3400-3295 cm-1

is arising from overlap of

stretching vibrations of coordinated water molecule with ν(N-H) of ligands are observed

in almost all of the complexes.53

Thus, the infrared spectra reveal that Schiff base

ligands are uninegatively bidentate, coordinating through phenolic O and azomethine N.

The infrared spectral bands are summarized in Table 5.IV.

220

Table: 5.IV. Infrared spectral band (cm-1

) of the Schiff bases derived from sulphadrugs and various aldehydes and their ruthenium(III)

complexes.

Compound ν(NH)/ ν(OH) ν(C=N) ν(C-O) ν(Ru-N) ν(Ru-O) ν(Ru-Cl)

oVSaH 3400, 3050 1635 1359 - - -

oVSmrzH 3250, 3125 1630 1360 - - -

SdSaH 3200, 3065 1622 1370 - - -

SdSmrzH 3340, 3180 1630 1355 - - -

2hNSaH 3230, 3060 1615 1368 - - -

2hNSmrzH 3239, 3040 1620 1370 - - -

[Ru(oVSa)2(H2O)Cl] 3130 1593 1345 490 440 365

[Ru(oVSmrz)2(H2O)Cl] 3120 1610 1340 485 445 360

[Ru(SdSa)2(H2O)Cl] 3160 1615 1350 500 460 355

[Ru(SdSmrz)2(H2O)Cl] 3140 1620 1342 490 452 370

[Ru(2hNSa)2(H2O)Cl] 3100 1600 1355 480 450 365

[Ru(2hNSmrz)2(H2O)Cl] 3115 1595 1345 482 455 380

221

Where,

oVSaH = Schiff base derived from o-Vanillin and sulphanilamide

oVSmrzH = Schiff base derived from o-Vanillin and sulphamerazine

SdSaH = Schiff base derived from Salicylaldehyde and sulphanilamide

SdSmrzH = Schiff base derived from Salicylaldehyde and sulphamerazine

2hNSaH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphanilamide

2hNSmrzH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphamerazine

222

PROTON MAGNETIC RESONANCE SPECTRAL STUDIES

A survey of literature revealed that the 1H NMR spectroscopy has been proved

useful in establishing the nature and structure of Schiff bases in solutions. The 1H NMR

spectrum of Schiff bases were recorded in CDCl3 solution using tetramethylsilane

(TMS) as internal standard. The signals due to phenolic-OH protons of the ligands

appear at ca. δ12.86-12.94 ppm. The signals at ca. δ8.09-8.64 ppm appear due to

azomethine protons (-CH=N). The ligands show a complex multiplet in the region ca.

δ6.84-7.86 ppm for the aromatic protons. In addition, signals appear in the ligands due

to various groups e.g. at ca. δ10.22-10.52 ppm due to NH protons and at ca. δ3.4 due to

protons of methoxy group. The 1H NMR spectra of the Schiff bases and the chemical

shifts of various types of protons are summarized in Table 5.V.

223

Table: 5.V. Proton magnetic resonance spectral data (δ, ppm) of the Schiff bases derived from sulphadrugs and various aldehydes.

Compounds δ(OH) δ(SO2NH) δ(N=CH) δ(Ar-H)

oVSaH 12.92 10.22 8.29 (s) 6.84 (m)

oVSmrzH 12.44 10.26 8.56 (s) 7.86 (m)

SdSaH 12.83 10.34 8.58 (s) 7.82 (m)

SdSmrzH 12.46 10.35 8.64 (s) 7.06 (m)

2hNSaH 12.83 10.38 8.26 (s) 7.28 (m)

2hNSmrzH 12.94 10.52 8.09 (s) 7.82 (m)

Where,

oVSaH = Schiff base derived from o-Vanillin and sulphanilamide

oVSmrzH = Schiff base derived from o-Vanillin and sulphamerazine

SdSaH = Schiff base derived from Salicylaldehyde and sulphanilamide

SdSmrzH = Schiff base derived from Salicylaldehyde and sulphamerazine

2hNSaH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphanilamide

2hNSmrzH = Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulphamerazine

224

FAB MASS SPECTRAL STUDIES

Fast atom bombardment (FAB) is an ionization technique used in mass

spectrometry.54-56 Mass spectroscopy mainly applied in analyses of biomolecules has

been increasingly used as a powerful structure characterization technique in the

coordination chemistry. The mass spectra of the ligands and complexes are compared.

Their fragmentation revealed the exact composition of the compounds formed. Mass

spectra of the ligands namely oVSaH, oVSmrzH, SdSaH, SdSmrzH, 2hNSaH and

2hNSmrzH show molecular peak at m/z = 306, 398, 276, 368, 326 and 418 which

corresponds to their molecular weight. The molecular ion peaks for the complexes of

ruthenium(III) are observed at m/z = 768, 952, 708, 892, 808 and 988 they are in

good agreement with their molecular weights. Therefore above fragmentation pattern

complemented the exact composition of the various compounds and described the

stoichiometry in which complexes has been formed.

THERMAL STUDIES

The presence of one water molecule and chloride ion in the coordination

sphere of the complexes suggested from infrared spectra is confirmed by TG and

DTG data. Ruthenium(III) complexes lose their weight and become stable in the

temperature range 150-260˚C corresponding to one water molecule and from 280-

330˚C a mass loss is attributed to the loss of chloride ion. The organic moiety such as

ligand decomposed further with the increasing temperature. Although decomposed

fragments of the ligand could not be approximated owing to continuous weight loss,

the complete decomposition of the ligand occurred at ~630˚C in all the complexes.

The final decomposition favours a mixed residue of Ru2O3-RuO2 at 680-695˚C. Thus,

the decomposition pattern obtained from TG curve confirms the proposed formulation

of the complexes.

225

On the basis of the above spectral studies the following structures are

suggested for the complexes.

CH

O

OCH3

N S

O

O

NHR"

RuH2O

CH

O

OCH3

NS

O

O

R"HN

Cl

CH

O

N S

O

O

RuH2O

CH

O

NS

O

O

Cl

NHR"

R"HN

226

CH

O

N S

O

O

NHR"

RuH2O

CH

O

NS

O

O

Cl

R"HN

Where,

R” = H; N

N CH3

Fig. 2: Proposed structure of metal complexes

CONCLUSIONS

The monobasic bidentate Schiff base ligands were found to be coordinated with

ruthenium(III) through phenolic oxygen and azomethine nitrogen and gave complexes

of the type [Ru(L)2(H2O)Cl]. The characteristics of the compounds have been studied

by various physiochemical data. A tentative octahedral structure have been proposed for

the complexes, where the ruthenium atom surrounded by different atoms showing six

coordination numbers.

227

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230

CHAPTER 6

Isatin, its Schiff and mannich bases are reported to show a variety of biological

activities such as antibacterial, antifungal and anti-HIV activities.1-4

Schiff bases are

important class of ligands in coordination chemistry and their complexing ability

containing different donor atoms is widely reported.5-7

Transition metal complexes of

Schiff bases have been amongst the most widely studied coordination in the past few

years due to their preparative accessibility, diversity and structural variability.8-14

Mixed ligand ruthenium and rhodium complexes, by virtue of their wide range of

reversible and accessible oxidation states, have proved to be useful catalysts,15-18

in

reactions such as hydrogenation, oxidation, carbonylation, hydroformylation etc. We

are interested in the reactivity properties of mononuclear ligand bridged where

cooperative features may enhance reactivity of individual sites. To this end we are

developing synthetic methodologies and investigating the properties of a series of

complexes containing ruthenium and rhodium. The interest in the study of these

Schiff bases has been growing due to their use in biological systems and analytical

chemistry.19,20

Dithiooxamide is an effective flexidentate complexing agent with

varied coordination chemistry. Due to the intense chromophoric character,

dithiooxamide can be used in an imaging processes,21

coordination polymers22

and

histological agents and as a source for duplicating processes.23

The Schiff bases of

dithiooxamide and their complexes have received most of the attention because of the

semiconductor, magnetic and spectroscopic properties.24,25

The aim of this work is to

synthesize and study the coordination behavior of the new Schiff and Mannich base

ligands. The chosen organic compound dithiooxamide is rich in electrons due to the

existence of nitrogen and sulphur atoms forming the desired dithiooxamide-metal

complexes. Coordination compounds of ruthenium(III) and rhodium(III) metals were

231

subjected to several studies concerning chemical behaviour such as electrical

conductivity, catalyses, electronic properties and their potential role in medical

applications.26, 27

Literature survey reveals that a number of complexes with ligands have been

reported for a variety of transition metals which shows interesting biological

properties.28-31

On account of these interesting structural and biological features

shown by isatin derived Schiff mannich base and its transition metal complexes. The

present study condensation reactions of Mannich bases N-morpholino methylisatin,

N-diphenylaminomethylisatin, N-methylisatin, N-acetylisatin, N-benzylisatin with

dithiooxamide. In this chapter the syntheses and spectral characterization of the

ruthenium(III) and rhodium(III) complexes of the formula [M(LH)2Cl2]Cl where M =

Ru(III) and Rh(III), with Schiff mannich bases derived from various substituted isatin

and dithiooxamide, LH = N-morpholino methylisatin (MrdtoII), N-

diphenylaminomethylisatin (DpdtoII), N-methylisatin (NMydtoII), N-acetylisatin

(NAydtoI), N-benzylisatin (NBydtoI) are described.

The structures of various ligands, used for the present study are shown below:

N

N CC

S

NH2

S

O

CH2R

232

R LH

O N

MrdtoII

PhN

Ph

DpdtoII

H NMydtoII

CH3

NAydtoI

NBydtoI

Fig. 1: Structure of ligands

6.1. EXPERIMENTAL

The synthesis of Schiff base ligands are given in chapter 3.

Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base derived

from isatin and dithiooxamide.

(i) Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base

derived from 1-morpholinomethyl imino isatin and dithiooxamide

(MrdtoII).

To a hot solution of Schiff mannich base ligand (0.696 g, 0.002 mol) in

ethanol (10 cm3) was slowly added a methanolic solution (5 cm

3) of ruthenium

trichloride (0.130 g, 0.001 mol). The reaction mixture was refluxed 3 hours on water

bath with constant stirring (pH 6-7). The volume of complex mixture was reduced to

1/4th

by evaporation and poured in ice cold water to yield precipitate. The orange to

brownish black colored complex precipitate was obtained. The desired product was

233

filtered and dried in vacuum over calcium chloride. Purity of the product was detected

by TLC. The yield was 38%.

Similarly methods have been adopted to get complex of rhodium trichloride

with schiff mannich base ligand. The orange to brown color complex precipitate was

obtained. The yield was 30%.

(ii) Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base

derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

(DpdtoII).

To a ethanolic solution of Schiff mannich base ligand (0.891 g, 0.002 mol) in

ethanol (10 cm3) was slowly added a methanolic solution (5 cm

3) of ruthenium

trichloride (0.130 g, 0.001 mol). The reaction mixture was refluxed 5 hours on water

bath with constant stirring (pH 6-7). The volume of complex mixture was reduced to

1/4th

by evaporation and poured in ice cold water to yield precipitate. The orange to

brown colored complex precipitate was obtained. The desired product was filtered and

dried in vacuum over calcium chloride. Purity of the product was detected by TLC.

The yield was 36%.

Similarly methods have been adopted to get complex of rhodium trichloride

with Schiff mannich base ligand. The orange to dark brown color complex precipitate

was obtained. The yield was 37%.

(iii) Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base

derived from N-methyl isatin and dithiooxamide (NMydtoII).

To a ethanolic solution of Schiff mannich base ligand (0.530 g, 0.002 mol) in

ethanol (10 cm3) was slowly added a methanolic solution (5 cm

3) of ruthenium

trichloride (0.130 g, 0.001 mol). The reaction mixture was refluxed 6 hours on water

234

bath with constant stirring (pH 6-7). The volume of complex mixture was reduced to

1/4th

by evaporation and poured in ice cold water to yield precipitate. The orange to

brown colored complex precipitate was obtained. The desired product was filtered and

dried in vacuum over calcium chloride. Purity of the product was detected by TLC.

The yield was 38%.

Similarly methods have been adopted to get complex of rhodium trichloride

with Schiff mannich base ligand. The orange to dark brown color complex precipitate

was obtained. The yield was 41%.

(iv) Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base

derived from N-acetyl isatin and dithiooxamide (NAydtoII).

To a ethanolic solution of Schiff mannich base ligand (0.586 g, 0.002 mol) in

ethanol (10 cm3) was slowly added a methanolic solution (5 cm

3) of ruthenium

trichloride (0.130 g, 0.001 mol). The reaction mixture was refluxed 6 hours on water

bath with constant stirring (pH 6-7). The volume of complex mixture was reduced to

1/4th

by evaporation and poured in ice cold water to yield precipitate. The orange to

brown colored complex precipitate was obtained. The desired product was filtered and

dried in vacuum over calcium chloride. Purity of the product was detected by TLC.

The yield was 28%.

Similarly methods have been adopted to get complex of rhodium trichloride

with Schiff mannich base ligand. The orange to dark brown color complex precipitate

was obtained. The yield was 30%.

235

(v) Ruthenium(III) and Rhodium(III) complexes with Schiff mannich base

derived from N-benzyl isatin and dithiooxamide (NBydtoI).

To a ethanolic solution of Schiff mannich base ligand (0.678 g, 0.002 mol) in

ethanol (10 cm3) was slowly added a methanolic solution (5 cm

3) of ruthenium

trichloride (0.130 g, 0.001 mol). The reaction mixture was refluxed 6 hours on water

bath with constant stirring (pH 6-7). The volume of complex mixture were reduced to

1/4th

by evaporation and poured in ice cold water to yield precipitate. The orange to

brown color complex precipitate was obtained. The desired product was filtered and

dried in vacuum over calcium chloride. Purity of the product was detected by TLC.

The yield was 35%.

Similarly methods have been adopted to get complex of rhodium trichloride

with Schiff mannich base ligand. The orange to dark brown color complex precipitate

was obtained. The yield was 30%.

All the reactions and analytical data are summarized in Table 6.I and Table

6.II.

236

Table: 6.I. Reactions of ruthenium(III) and rhodium(III) chloride with Schiff mannich bases derived from isatin and dithiooxamide.

Reactants Molar

ratio

Stirring/

Refluxing

time (hrs)

Product Colour Decomp.

Temp. (˚C)

Yield (%)

RuCl3∙3H2O + MrdtoII 1:2 3 [Ru(MrdtoII)2Cl2]Cl Brownish black 250 38

RuCl3∙3H2O + DpdtoII 1:2 5 [Ru(DpdtoII)2Cl2]Cl Black 252 36

RuCl3∙3H2O + NMydtoII 1:2 6 [Ru(NMydtoII)2Cl2]Cl Brown 258 38

RuCl3∙3H2O + NAydtoI 1:2 6 [Ru(NAydtoI)2Cl2]Cl Brown 256 28

RuCl3∙3H2O + NBydtoI 1:2 6 [Ru(NBydtoI)2Cl2]Cl Brown 260 35

RhCl3∙3H2O + MrdtoII 1:2 3 [Rh(MrdtoII)2Cl2]Cl Dark brown 250 30

RhCl3∙3H2O + DpdtoII 1:2 6 [Rh(DpdtoII)2Cl2]Cl Black 260 37

RhCl3∙3H2O + NMydtoII 1:2 19 [Rh(NMydtoII)2Cl2]Cl Brown 262 41

RhCl3∙3H2O + NAydtoI 1:2 18 [Rh(NAydtoI)2Cl2]Cl Black 264 30

RhCl3∙3H2O + NBydtoI 1:2 20 [Rh(NBydtoI)2Cl2]Cl Dark brown 252 30

237

Where,

MrdtoII = Schiff mannich base derived from 1-morpholinomethyl imino isatin and dithiooxamide

DpdtoII = Schiff mannich base derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

NMydtoII = Schiff mannich base derived from N-methyl isatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetyl isatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzyl isatin and dithiooxamide

238

Table: 6.II. Analytical data of ruthenium(III) and rhodium(III) complexes with Schiff mannich bases derived from isatin and

dithiooxamide.

Complexes M.Wt.

Found (Calcd.)

Analysis found (calcd.)%

C H N S Cl M

[Ru(MrdtoII)2Cl2]Cl 895

(896.3)

41.32

(41.12)

2.15

(2.69)

11.25

(12.50)

13.15

(14.31)

10.62

(11.86)

10.70

(11.27)

[Ru(DpdtoII)2Cl2]Cl 1067

(1068.5)

50.20

(51.70)

2.22

(3.39)

10.20

(10.48)

11.82

(12.00)

8.05

(9.95)

8.62

(9.45)

[Ru(NMydtoII)2Cl2]Cl 733

(734.2)

35.28

(35.99)

2.32

(2.47)

10.90

(11.44)

16.94

(17.47)

14.10

(14.48)

12.10

(13.76)

[Ru(NAydtoI)2Cl2]Cl 789

(790.2)

36.20

(36.48)

2.10

(2.29)

10.90

(10.63)

14.83

(16.23)

12.48

(13.46)

11.10

(12.79)

[Ru(NBydtoI)2Cl2]Cl 885

(886.3)

45.45

(46.07)

2.30

(2.95)

9.12

(9.48)

13.68

(14.47)

11.05

(12.00)

10.38

(11.04)

[Rh(MrdtoII)2Cl2]Cl 897

(898.2)

38.50

(40.12)

2.50

(2.69)

12.00

(12.47)

13.92

(14.27)

10.10

(11.84)

10.18

(11.48)

[Rh(DpdtoII)2Cl2]Cl 1069

(1070.3)

50.08

(51.61)

3.10

(3.39)

10.20

(10.46)

10.26

(11.98)

9.15

(9.93)

8.72

(9.61)

239

[Rh(NMydtoII)2Cl2]Cl 734

(735.9)

34.98

(35.90)

2.25

(2.46)

10.20

(11.41)

17.22

(17.42)

14.32

(14.45)

12.66

(13.98)

[Rh(NAydtoI)2Cl2]Cl 790

(791.9)

35.82

(36.39)

2.20

(2.29)

10.46

(10.61)

16.08

(16.19)

13.11

(13.42)

11.64

(12.99)

[Rh(NBydtoI)2Cl2]Cl 887

(888.2)

44. 22

(45.98)

2.90

(2.95)

8.88

(9.46)

13.55

(14.44)

10.75

(11.97)

10.26

(11.58)

Where,

MrdtoII = Schiff mannich base derived from 1-morpholinomethyl imino isatin and dithiooxamide

DpdtoII = Schiff mannich base derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

NMydtoII = Schiff mannich base derived from N-methyl isatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetyl isatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzyl isatin and dithiooxamide

240

6.2. RESULT AND DISCUSSION

The synthesis of the new ligands has been achieved by the reaction of Schiff

mannich base precursor of isatin followed by condensation with dithiooxamide. The

physical and analytical data of Schiff mannich bases derived from various isatin and

dithiooxamide and their complexes are given in Table 6.I and 6.II. All the

ruthenium(III) and rhodium(III) complexes are brown to blackish brown in color.

They are soluble in ethanol, tetrahydrofuran, dimethylformamide and

dimethylsulphoxide while insoluble in water. The molar conductance values of the

complexes in DMF (10-3

M) solutions showing the 1:1 electrolytic nature.32

The low

yield resulted from extensive purification of products from the starting materials as

was indicated from TLC result.

RuCl3∙3H2O + 2LH → [Ru(LH)2Cl2]Cl

RhCl3∙3H2O + 2LH → [Rh(LH)2Cl2]Cl

Where, LH = MrdtoII, DpdtoII, NMydtoI, NAydtoI, NBydtoI

MAGNETIC MOMENT

The magnetic moments of the ruthenium(III) complexes are reported in Table

6.III. The room temperature magnetic moments of the ruthenium(III) complexes lie in

the range 1.80-2.02 B.M., which are expected to be lower than the predicted value of

2.10 B.M. They are near spin only value suggesting t2g5

(low spin, d5, S = 1/2)

configuration with one unpaired electron. The complexes of rhodium(III) are

diamagnetic (low spin, d6, S = 0) as expected. This is consistent with an octahedral

arrangement of nitrogen and sulphur atoms producing a strong field.33,34

241

ELECTRONIC SPECTRAL STUDIES

Ruthenium(III) complexes act as paramagmetic one and rhodium(III)

complexes are diamagnetic. The electronic spectra of all ruthenium(III) complexes

show three d-d bands, corresponding to transitions 2T2g →

4T1g,

2T2g →

4T2g,

2T2g →

2A2g,

2T1g display bands at 13510-14000, 17240-18300 and 23460-23800 cm

-1. The

electronic spectra of the rhodium(III) complexes exhibited bands at 17060-17640,

20220-20890 and 27300-28590 cm-1

in the spectrum. The ground state in rhodium(III)

complexes in an octahedral field is 1A1g. Thus, the possible transitions in the

rhodium(III) complexes are 1A1g →

3T1g,

1A1g →

1T1g and

l A1g →

1T2g of d-d origin.

The general pattern of the spectra indicates octahedral geometry around the metal

ions.35,36

The electronic spectral bands with assignments for ruthenium(III) and

rhodium(III) complexes are summarized in Table 6.III.

242

Table: 6.III. Magnetic moment and electronic spectral data of ruthenium(III) and rhodium(III) complexes with Schiff mannich bases

derived from isatin and dithiooxamide.

Complexes λmax (cm-1

) Assignments µeff (B.M.)

[Ru(MrdtoII)2Cl2]Cl 13700

17240

23600

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.80

[Ru(DpdtoII)2Cl2]Cl 13520

17310

23540

-do- 2.02

[Ru(NMydtoII)2Cl2]Cl 13620

17930

23460

-do- 1.92

[Ru(NAydtoI)2Cl2]Cl 14000

18300

23580

-do- 1.98

[Ru(NBydtoI)2Cl2]Cl 13510

18030

23800

-do- 1.86

243

[Rh(MrdtoII)2Cl2]Cl 17060

20210

27180

1A1g →

3T1g

1A1g→

1T1g

1A1g→

1T2g

Dia.

[Rh(DpdtoII)2Cl2]Cl 17550

20280

27400

-do- Dia.

[Rh(NMydtoII)2Cl2]Cl 17300

20220

27300

-do- Dia.

[Rh(NAydtoI)2Cl2]Cl 17400

20380

28020

-do- Dia.

[Rh(NBydtoI)2Cl2]Cl 17640

20890

28590

-do- Dia.

244

Where,

MrdtoII = Schiff mannich base derived from 1-morpholinomethyl imino isatin and dithiooxamide

DpdtoII = Schiff mannich base derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

NMydtoII = Schiff mannich base derived from N-methyl isatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetyl isatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzyl isatin and dithiooxamide

245

INFRARED SPECTRAL STUDIES

The infrared spectra of the ligands display two sharp bands in the region

3210-3260 cm-1

and 3320-3430 cm-1

assignable to νsym and νasym vibrations of the

NH2 group, respectively.

37 The complexes exhibited shifts of the thioamide groups to

lower frequencies indicating the involvement of thiocarbonyl sulphur atoms in

coordination with these metal ions.38

The spectra of complexes demonstrated further

shift of NH2 group vibration modes to lower frequencies as a result of bonding.39

On

the other hand the spectra of complexes displayed the disappearance of the stretching

mode of thioamide NH2 group and the shift of C-S band to lower frequencies. This

refers to the bonding of metal ion to the ligand in the form of in the

complexes. The appearance of stretching modes assigned to NH and C=N of −C=NH

groups was observed at 3120-3200 and 1614-1650 cm−1

, respectively.40

The stretching

vibrations of azomethine group of the Schiff base ligands were shifted to lower

frequencies in all spectra whereas stretching vibrations of carbonyl group were shifted

to lower frequencies in all spectra indicating additional coordination of metal ions to

C=N groups. The IR spectra showed that the ligands exhibited vibrational modes

of νC=N of azomethine group, (νC–N, νNH), (νC–N, νC–S), νC–S,

and νC=S of dithiooxamide moiety.41

The position of the bands assigned

to νNH vibrations of the cyclic rings was dependent on their environment, νNH of

ligands were observed at lower frequencies compared with that of ligands. The

complexes showed additional shifts in νNH to lower frequencies while no significant

changes were observed on vibration modes of C=O group which rules out

coordination with carbonyl oxygen.42,43

Shifts of thioamide bands were observed in

246

the spectra of complexes and were attributed to coordination of metal ion with sulphur

atom. This may be attributed to cleavage of thioamide ring on complexation leading

reappearance of νC=O and νNH2 of isatin and dithiooxamide moieties, respectively.

Additional bands were observed at ca. 1650 and ca. 880 cm-1

assigned to

νC=N (azomethine) and νC=S in all complexes respectively, which remain at almost

the same positions in the spectra of the complexes suggesting that not involved in

chelation.44

The complex exhibited shift of νC=S band to lower frequency which

refers to coordination of sulphur to ruthenium(III) and rhodium(III) ions.45

The

appearance of medium intensity bands at ca. 530, 435 and 312 cm-1

region assignable

to νM-N, νM-S and νM-Cl vibrations, respectively. The appearance of the non-ligand

bands further support the bonding of the ligands to the metals through the nitrogen,

sulphur and chloride.46-51

The infrared spectral bands of the ligands and their corresponding complexes

are summarized in Table 6.IV.

247

Table: 6.IV. Infrared spectral band (cm-1

) of the Schiff mannich bases derived from isatin and dithiooxamide and their ruthenium(III)/

rhodium(III) complexes.

Compound ν(NH2) ν(C=NH) ν(C=N) ν(C=S) ν(M-N) ν(M-S) ν(M-Cl)

MrdtoII 3240, 3430 - 1614 857 - - -

DpdtoII 3260, 3420 - 1619 858 - - -

NMydtoII 3210, 3320 - 1615 858 - - -

NAydtoI 3235, 3310 - 1620 859 - - -

NBydtoI 3230, 3315 - 1640 869 - - -

[Ru(MrdtoII)2Cl2]Cl - 3120 1614, 1640 845 520 440 310

[Ru(DpdtoII)2Cl2]Cl - 3140 1637, 1639 835 560 452 312

[Ru(NMydtoII)2Cl2]Cl - 3185 1638, 1640 840 535 410 298

[Ru(NAydtoI)2Cl2]Cl - 3200 1630, 1650 833 540 450 305

[Ru(NBydtoI)2Cl2]Cl - 3160 1618, 1635 850 532 430 312

[Rh(MrdtoII)2Cl2]Cl - 3165 1615, 1640 836 530 435 298

248

[Rh(DpdtoII)2Cl2]Cl - 3145 1620, 1650 840 545 415 310

[Rh(NMydtoII)2Cl2]Cl - 3155 1630, 1645 845 530 418 306

[Rh(NAydtoI)2Cl2]Cl - 3160 1615, 1635 850 520 425 304

[Rh(NBydtoI)2Cl2]Cl - 3125 1620, 1640 855 560 400 312

Where,

MrdtoII = Schiff mannich base derived from 1-morpholinomethyl imino isatin and dithiooxamide

DpdtoII = Schiff mannich base derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

NMydtoII = Schiff mannich base derived from N-methyl isatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetyl isatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzyl isatin and dithiooxamide

249

PROTONIC MAGNETIC RESONANCE SPECTRAL STUDIES

The proton magnetic resonance spectra of ligands and their corresponding

rhodium(III) complexes have been recorded in DMSO-d6. The intensities of all the

resonance lines were determined by planimetric integration. The -NH2 group gives a

sharp singlet at δ2.48-2.60 ppm in the free ligands. The signal due to NH protons

appeared in the lower field at δ9.84-10.62 ppm as singlet. The multiplets in range of

δ6.40-7.82 ppm assigned to aromatic protons have been observed in ligands as well as

in complexes. Other signals appeared in the spectra of ligands and complexes are at

δ2.15-2.24 ppm as a singlet due to methyl and at δ3.43-3.66 ppm due to methylene.

The data regarding various peaks are summarized in Table 6.V.

250

Table: 6.V. Proton magnetic resonance spectral data (δ, ppm) of the Schiff mannich bases derived from isatin and dithiooxamide and

their rhodium(III) complexes.

Compounds δ(NH2)/ δ(N-H) δ(CH2) δ(CH3) δ(Ar-H)

MrdtoII 2.58 (b) 3.60 (s) - 6.92 (m)

DpdtoII 2.48 (b) 3.43 (s) - 7.82 (m)

NMydtoII 2.56 (b) - 2.15 7.26 (m)

NAydtoI 2.60 (b) - 2.20 7.08 (m)

NBydtoI 2.54 (b) 3.47 (s) - 7.28 (m)

[Rh(MrdtoII)2Cl2]Cl 9.88 (b) 3.66 (s) - 7.08 (m)

[Rh(DpdtoII)2Cl2]Cl 9.84 (b) 3.59 (s) - 7.29 (m)

[Rh(NMydtoII)2Cl2]Cl 9.66 (b) - 2.24 7.82 (m)

[Rh(NAydtoI)2Cl2]Cl 10.08 (b) - 2.22 7.80 (m)

[Rh(NBydtoI)2Cl2]Cl 10.62 (b) 3.64 (s) - 7.82 (m)

251

Where,

MrdtoII = Schiff mannich base derived from 1-morpholinomethyl imino isatin and dithiooxamide

DpdtoII = Schiff mannich base derived from 1-diphenylaminomethyl imino isatin and dithiooxamide

NMydtoII = Schiff mannich base derived from N-methyl isatin and dithiooxamide

NAydtoI = Schiff mannich base derived from N-acetyl isatin and dithiooxamide

NBydtoI = Schiff mannich base derived from N-benzyl isatin and dithiooxamide

252

On the basis of the above analytical and spectral data the structure may be

tentatively proposed for ruthenium(III) and rhodium(III) complexes.

N

N C C

S

O

CH2R

SH

NHM

N

NCC

S

O

H2C R

HS

HNCl

Cl

Cl

Where,

M = Ru(III), Rh(III)

R = O N

, N

Ph

Ph , H, CH3,

Fig. 2: Praposed structure of complexes

CONCLUSIONS

On the basis of the analytical data and spectral studies, it has been observed

that the ligands coordinated to the metal atoms as a neutral bidentate manner through

sulphur and nitrogen. The bonding modes of ligand via imine nitrogen and sulphur

atoms have been deduced by spectral findings. The overall octahedral geometry

around the respective metal ions has been drawn on the basis of electronic spectra and

magnetic moment studies.

253

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257

CHAPTER 7

Heterocyclic hydrazones form an important class of compounds with a wide

spectrum of biological applications like their antimicrobial, antitubercular and

antitumor activities.1,2

The chemistry of coordination compounds with Schiff base as

part of their complex structure extends from dinuclear discrete molecule to

polynuclear species. Metal complexes of Schiff bases have played a pivotal role in the

field of coordination chemistry. The ligation of Schiff bases towards the central metal

ion provides extra stability and versatility of compounds making a greater choice of

flexibility. The importance of heterocyclic hydrazones in the designing of new drugs

is mainly attributed to the presence of the heterocyclic nucleus and the azomethine

>N-N=C<. Through research in the field of Schiff base metal complexes have been

achieved, isolation of complexes with new ligands has been an ongoing area of

interest in research.3-5

Though a number of medicines are available for the treatment

of hazardous diseases like tumour and tuberculosis, scientific world is still in search

of compounds that have lesser side effects and are effective against such diseases.6-9

Isoniazid, a heterocyclichydrazide with nitrogen as hetero atom was reported

to possess very high in vivo inhibitory activity drugs used in the treatment of

tuberculosis, but the presence of free-NH2 group in isoniazid leads to hepato toxicity

on chronic use. In continuation of these series of investigation, at tempts have been

made to widen the scope of derivatization by providing more flexibility through

Schiff base formation with isoniazid containing an amino group and complexation

with metal ions.10-12

Now a days ruthenium chelates appears to be most promising due

to availability of its various oxidation states. Their bioactivity has been attributed to

their complexation ability with the metal ions, which of course, increase the

lipoplicity of the complexes, facilitating the transport of metal ion through the cell

258

membrane. As the use of aroylhydrazone complexes in a given reactions depends to a

great extent on their molecular structure, the structure of ruthenium chelate with aryl

hydrazones drew the attention of many investigators.13-16

Ruthenium(III) and

iridium(III) complexes, by virtue of their wide range receives ample attention due to

the fascinating properties of reversible and accessible oxidation states. Dinuclear

ruthenium(III) and iridium(III) complexes are contemporary relevance due to their

magnetic, catalytic and electron transfer properties and models of bioinorganic

chemistry. It was also reported that ruthenium complexes of isoniazid possess

antitumor and antitubercular activities respectively. With this perspective we had

synthesised a heterocyclic hydrazone, 2-hydroxy benzaldehyde

isonicotinoylhydrazone (HBINH), o-vanillin isonicotinoylhydrazone (o-VINH), 2-

hydroxyacetophenone isonicotinoylhydrazone (2-HAINH), 5-chlorosalicylaldehyde

isonicotinoylhydrazone (5-CSINH) and its ruthenium(III) and iridium(III) complexes.

These ligands containing an amide bond and capable of undergoing keto enol

tautomerism can coordinate to metal atom through nitrogen or through oxygen or

simultaneously through nitrogen and oxygen both. The coordination behaviour of

ligands depends upon the pH of the medium, nature of the substituent and position of

the hydrazone group relative to the pyridine nitrogen.17-20

In this chapter, the synthesis

and structural studies of ruthenium(III) and iridium(III) complexes with hydrazones

derived from various aldehydes/ ketones and isonicotinoyl hydrazide are described.

The structure of ligand used for the present study, is shown below.

259

N

C

O N NH2

H

+

C

O X

OH

N

C

O N N

H

C

X

OH

EthanolReflux

N

C

OH N N C

X

OH

Y

Z

YZ

Y

Z

260

Fig. 1: Structure of ligands

7.1. EXPERIMENTAL

The synthesis of hydrazone ligands are given in chapter 3.

Ruthenium(III) and Iridium(III) complexes with hydrazones derived from

isoniazid and various aldehydes/ ketones

(i) Synthesis of Ruthenium(III) and Iridium(III) complex with hydrazone

derived from isoniazid and 2-hydroxybenzaldehyde (HBINH) in 1:1 ratio.

A solution of RuCl3·3H2O (0.130 g, 0.01 mol) in ethanol 50 ml was taken in

round bottom flask. In this ethanolic solution of ligand HBINH (0.120 g, 0.01 mol)

was suspended. The reaction mixture was refluxed at room temperature with constant

stirring under 3 hours. Instant changed in colour brown to black. The black coloured

complex precipitated, after that volume of solution was reduced to 1/4th

of its volume

and poured in ice cold water to yield precipitate. As on complete of reaction black

colour product formed it was filtered off and finally dried in vacuum over fused

calcium chloride in order to get desired product. The yield was 62%.

Iridium(III) complex was also synthesized in same ratio (1:1) as ruthenium

complex except that after refluxing 4 hours, the solution volume was reduced to 75%

by evaporation and the residue was left to stand in ice cold water. After that brown

x y z Abbreviation

H H H L1H2 (HBINH)

H OCH3 H L2H2 (o-VINH)

CH3 H H L3H2 (2-HAINH)

H H Cl L4H2 (5-CSINH)

261

solid was obtained and filtered under vacuum, wash with minimum volume of

distilled water and then dried in vacuum over calcium chloride. The yield was 70%.

(ii) Synthesis of Ruthenium(III) and Iridium(III) complexes with hydrazone

derived from isoniazid and o-vanillin (o-VINH) in 1:1 ratio.

A solution of RuCl3∙3H2O (0.130 g, 0.01 mol) in ethanol 50 ml was taken in

round bottom flask. In this ethanolic solution of ligand o-VINH (0.135 g, 0.01 mol)

was suspended. The reaction mixture was refluxed at room temperature with constant

stirring under 3 hours. Instant change in colour brown to black. The black coloured

complex precipitated, after that volume of solution was reduced to 1/4th

of its volume

and poured in ice cold water to yield precipitate. As on complete of reaction black

colour product formed it was filtered off and finally dried in vacuum over fused

calcium chloride in order to get desired product. The yield was 72%.

Iridium(III) complex was also synthesized in same ratio (1:1) as ruthenium

complex expect that after refluxing 4 hours, the solution volume was reduced to 75%

by evaporation and the residue was left to stand in ice cold water. After that dark

brown solid was obtained and filtered under vacuum, wash with minimum volume of

distilled water and then dried in vacuum over calcium chloride. The yield was 68%.

(iii) Synthesis of Ruthenium(III) and Iridium(III) complex with hydrazone

derived from isoniazid and 2-hydroxyacetophenone (2-HAINH) in 1:1

ratio.

A solution of RuCl3·3H2O (0.130 g, 0.01 mol) in ethanol 50 ml was taken in

round bottom flask. In this ethanolic solution of ligand 2-HAINH (0.127 g, 0.01 mol)

was suspended. The reaction mixture was refluxed at room temperature with constant

262

stirring under 4 hours. Instant changed in colour brown to black. The black coloured

complexes precipitated, after that volume of solution was reduced to 1/4th

of its

volume and poured in ice cold water to yield precipitate. As on complete of reaction

black colour product formed it was filtered off and finally dried in vacuum over fused

calcium chloride in order to get desired product. The yield was 65%.

Iridium(III) complex was also synthesized in same ratio (1:1) as ruthenium

complex except that after refluxing 4 hours, the solution volume was reduced to 75%

by evaporation and the residue was left to stand in ice cold water. After that mud

brown solid was obtained and filtered under vacuum, wash with minimum volume of

distilled water and then dried in vacuum over calcium chloride. The yield was 68%.

(iv) Synthesis of Ruthenium(III) and Iridium(III) complex with hydrazone

derived from isoniazid and 5-chlorosalicylaldehyde (5-CSINH) in 1:1 ratio.

A solution of RuCl3·3H2O (0.130 g, 0.01 mol) in ethanol 50 ml was taken in

round bottom flask. In this ethanolic solution of ligand 5-CSINH (0.137 g, 0.01 mol)

was suspended. The reaction mixture was refluxed at room temperature with constant

stirring under 5 hours. Instant changed in colour brown to black. The black coloured

complex precipitated, after that volume of solution was reduced to 1/4th

of its volume

and poured in ice cold water to yield precipitate. As on complete of reaction black

colour product formed it was filtered off and finally dried in vacuum over fused

calcium chloride in order to get desired product. The yield was 68%.

Iridium(III) complex was also synthesized in same ratio (1:1) as ruthenium

complexes except that after refluxing 5 hours, the solution volume was reduced to

75% by evaporation and the residue was left to stand in ice cold water. After that

263

black solid was obtained and filtered under vacuum, wash with minimum volume of

distilled water and then dried in vacuum over calcium chloride. The yield was 72%.

All the reactions are summarized in their corresponding Table 7.I and

analytical data are given in Table 7.II.

264

Table: 7.I. Reactions of ruthenium(III) and iridium(III) chloride with hydrazones derived from isonicotinoyl hydrazide and various

aldehydes/ ketones.

Reactants Molar

ratio

Stirring/

Refluxing

time (hrs)

Product Colour Decomp.

Temp. (˚C)

Yield (%)

RhCl3∙3H2O + HBINH 1:1 3 [Ru(HBINH)(H2O)Cl]2 Black 265 62

RhCl3∙3H2O + o-VINH 1:1 3 [Ru(o-VINH)(H2O)Cl]2 Black 270 72

RhCl3∙3H2O + 2-HAINH 1:1 4 [Ru(2-HAINH)(H2O)Cl]2 Black 265 65

RhCl3∙3H2O + 5-CSINH 1:1 5 [Ru(5-CSINH)(H2O)Cl]2 Brown green 280 68

IrCl3∙3H2O + HBINH 1:1 4 [Ir(HBINH)(H2O)Cl]2 Brown >320 70

IrCl3∙3H2O + o-VINH 1:1 4 [Ir(o-VINH)(H2O)Cl]2 Dark Brown >345 65

IrCl3∙3H2O + 2-HAINH 1:1 4 [Ir(2-HAINH)(H2O)Cl]2 Mud brown >340 68

IrCl3∙3H2O + 5-CSINH 1:1 5 [Ir(5-CSINH)(H2O)Cl]2 Black >360 72

265

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

266

Table: 7.II. Analytical data of ruthenium(III) and iridium(III) chloride with hydrazones derived from isonicotinoyl hydrazide and

various aldehydes/ ketones.

Complexes M.Wt.

Found (Calcd.)

Analysis found (calcd.)%

C H N Cl M

[Ru(HBINH)(H2O)Cl]2 786

(787.5)

38.86

(39.65)

2.16

(2.81)

10.01

(10.67)

8.88

(9.00)

24.97

(25.66)

[Ru(o-VINH)(H2O)Cl]2 846

(847.6)

38.67

(39.67)

3.01

(3.09)

8.57

(9.91)

7.79

(8.36)

22.88

(23.84)

[Ru(2-HAINH)(H2O)Cl]2 814

(815.6)

40.32

(41.23)

3.15

(3.21)

10.15

(10.30)

7.89

(8.69)

23.11

(24.78)

[Ru(5-CSINH)(H2O)Cl]2 884

(785.5)

38.10

(39.75)

2.22

(2.56)

9.20

(10.69)

8.67

(9.02)

24.89

(25.73)

[Ir(HBINH)(H2O)Cl]2 615

(616.6)

34.90

(35.00)

2.30

(2.60)

7.90

(8.80)

28.20

(29.70)

15.20

(16.80)

267

[Ir(o-VINH)(H2O)Cl]2 630

(630.8)

35.60

(36.10)

2.20

(2.80)

7.20

(8.60)

29.20

(30.40)

15.20

(16.40)

[Ir(2-HAINH)(H2O)Cl]2 643

(644.7)

36.00

(37.20)

2.00

(2.10)

7.20

(8.40)

27.60

(28.00)

14.50

(15.90)

[Ir(5-CSINH)(H2O)Cl]2 664

(664.7)

38.60

(39.70)

2.05

(2.10)

7.60

(8.40)

27.90

(28.00)

14.20

(15.90)

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

268

7.2. RESULT AND DISCUSSION

The condensation reaction in 1:1 ratio of Isonicotinoyl hydrazide and various

aldehydes/ ketones viz. 2-hydroxybenzaldehyde, o-vanillin, 2-hydroxyacetophenone

and 5-chlorosalicylaldehyde has been carried out given potentially active tridentate

ligands. The metal complexes formed between metal trichloride and hydrazone have

stoichiometry [Ru(L)(H2O)Cl]2 and [Ir(L)(H2O)Cl]2. The reaction can be shown as

follows:

2MCl3∙3H2O + 2LH2 → [M(L)(H2O)Cl]2 + 4HCl

(M = Ru(III), Ir(III); LH2 = HBINH, o-VINH, 2-HAINH, 5-CSINH)

The analytical and physical data of the ligands and the complexes are in

agreement with their molecular formulae. All the complexes exhibit good solubility in

DMF, DMSO, THF and poor solubility in water. These complexes sparingly soluble

in methanol, ethanol. All complexes of isonicotinoyl hydrazones were obtained in

good yield and are stable in solid and liquid phase. Electrical conductance in DMF

solution indicated non-electrolytic nature of the complexes.

MAGNETIC MOMENT

The spin-only values were calculated using equation µRu-Ru = 2[µRu2 + µRu

2)]

1/2

and it lie in the range 0.72-1.02 B.M. range. These low values might be indicative of

metal-metal interactions in the dimeric structure. The effective magnetic moment of

complexes agreed well with that predicted for a low-spin d5

configuration.21

Ruthenium(III) ion in the complexes are in good agreement with their corresponding

spin-only value assuming no magnetic interaction between the metal ions. Therefore,

these data indicate that both ruthenium(III) metals are in low-spin states. The

269

complexes can be attributed to the setting in π-pathway of super exchange through

oxo-bridge. Upon heating the respective compounds to 200˚C in an air oven, there

were no weight losses suggesting the absence of water molecules in the crystal lattice.

This possibility mainly arisen due to the metal-metal interaction between ruthenium

ions22,23

suggested dinuclear configuration. It also confirmed that in dinuclear

complexes both of ruthenium metal is in low spin states.24

Iridium(III) complexes

shows zero magnetic moment at room temperature and suggest diamagnetic structure

with d6 paired electron (low spin, d

6 S = 0 ) as expected this with an octahedral

arrangement of donor atoms producing strong field.

ELECTRONIC SPECTRAL STUDIES

The complexes formed very intensely coloured solutions and thus very low

concentrations have been used. The electronic spectra of all ruthenium(III) complexes

were recorded in DMF solution and given in Table 7.III. All the ruthenium(III)

complexes are paramagnetic indicating the central metal atom in its +3 oxidation

state. Dimeric complexes showed three bands in the region of 13900-31260 cm-1

. The

electronic spectrum of ruthenium(III) complexes are often made up of well described

ligands to metal charge transfer bands. Ligand → metal charge transfers exhibit high

intensity bands and are observed at 13908-15350 cm-1

. Such high intensity bands

generally abscure the weak d-d transitions of the metal centers. Other bands observed

in ruthenium(III) complexes are in range 17260-20120 cm-1

and 26520-312060 cm-1

assigned to 2T2g →

4T2g and

2T2g →

4A2g transitions in increasing order of energy.

Complexes have shown the nearest coordination sphere with microsymmetry

octahedral. Since ruthenium(III) is a d5

system it has relatively high oxidizing

properties, the charge transfer bands of the Lπy → t2g type are prominent in the lower

energy region and it obscure the weaker bands due to d-d transition.25,26

It therefore

270

Table: 7.III. Magnetic moment and electronic spectral data of ruthenium(III) and iridium(III) with isonicotinoyl hydrazones derived

from various aldehydes/ ketones.

Complexes λmax (cm-1

) Assignments µeff (B.M.)

[Ru(HBINH)(H2O)Cl]2 13908, 17260, 26520 CT, 2T2g →

4T2g,

2T2g→

2A2g 0.86

[Ru(o-VINH)(H2O)Cl]2 15038, 20120, 30488 -do- 0.72

[Ru(2-HAINH)(H2O)Cl]2 15350, 17392, 30462 -do- 0.84

[Ru(5-CSINH)(H2O)Cl]2 14280, 17855, 31260 -do- 1.02

[Ir(HBINH)(H2O)Cl]2 18640, 29410, 39840 1A1g →

3T1g,

1A1g →

1T1g,

1A1g →

1T2g Dia.

[Ir(o-VINH)(H2O)Cl]2 18860, 31150, 40322 -do- Dia.

[Ir(2-HAINH)(H2O)Cl]2 18620, 29590, 39980 -do- Dia.

[Ir(5-CSINH)(H2O)Cl]2 20490, 32154, 41600 -do- Dia.

271

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

272

becomes difficult to assign conclusively the bands in the case of ruthenium(III)

complexes which appear in the visible region. The data27,28

concerning interpretation

of the absorption spectra of ruthenium(III) coordination compounds revealed low spin

states in all the complexes. Three charge transfer bands in close proximity with

data29,30

also proposed that central ion configuration d5 causes low spin states. Thus,

in this way all the observed values lie in the range of ligand to metal charge transfer

as depicted for ruthenium(III) octahedral complexes with heterocyclic ligands.31

The

observed values of 10 Dq are usually associated with considerable electron

delocalization as an overall effect of covalent bonding and were found higher in

range.32,33

Electronic spectra of all iridium(III) complexes exhibited bands at 18620-

20490 cm-1

, 29410-32154 cm-1

and 39840-41600 cm-1

corresponding to 1A1g →

3T1g,

1A1g →

1T1g, and

1A1g →

1T2g transitions in increasing order of energy. Thus, general

pattern of electronic spectra of the complexes indicates octahedral geometry around

metal ions, with donor atoms of nitrogen and oxygen types.34-36

INFRARED SPECTRAL STUDIES

The infrared spectra of metal complexes are very complicated. However,

attempts have been made to identify bands which provide vital information on the

mode of bonding of the ligand with the metals, by comparing their spectra with the

ligand and other related reported complexes. The spectra of ligands has bands at ca.

3185 cm-1

and ca. 1670 cm-1

corresponding to νΝ-H stretching and νC=O vibrations,

respectively. This may be assigned to the intermolecular hydrogen bonding involving

the phenolic OH and NH groups.37

All complexes exhibit a broad band relatively in

the region of higher frequency between 3400-3200 cm-1

indicating the presence of

273

coordinated water molecules in the complexes.38,39

The broadness of the band has

been assigned to the combined νH2O and νN-H stretching mode of vibrations. A

strong band is obtained in the region of ca. 1655 cm-1

in the complexes which may be

due to νC=N.40,41

The fundamental frequencies due to C-C and N-N have also been

observed in the range of 1025- 1055 cm-1

.42

An additional band appears in the range

3090-3065 cm-1

for νC-H (phenylic ring).43

These all the facts suggested enolic form

of the ligand in the solid state. The infrared spectra of the ligands and its binuclear

ruthenium(III) and iridium(III) complexes have been studied carefully. The presence

of medium to weak intensity broad band centered at 3430 cm-1

in the ligand

corresponds to phenolic ν(OH). In the spectra of the complexes, ν(OH) remain absent

while it is difficult to trace the disappearance of ν(OH) because the range of ν(OH)

group occurred at the same zone where ν(N-H) is located. This indicates the

deprotonation of the hydroxyl group and its coordination with metal ion and

confirmed out the mononegative behaviour of ligands.44

The broadening of ν(OH)

vibrations may be due to the overlapping with absorption due to coordinated water.

The band in binuclear complexes shift to lower frequency due to azomethine ν(C=N)

by 20-45 cm-1

suggest bonding through azomethine nitrogen.45-50

Coordination of the

nitrogen to the metal atom would be expected to reduce the electron density in the

azomethine links and this cause a shift in the ν(C=N) band.51,52

ν(N-N) band in

complexes exhibits the small shift to higher frequency at ca. 1050 cm-1

and further

indicated participation of azomethine nitrogen in coordination.53

In support of this

further structure was confirmed by the coordination of the ligands to metal atom by

appearance of the ν(M-N), ν(M-O) and ν(M-Cl) at range 480-520 cm-1

, 430-445 cm-1

and 350-380 cm-1

as additional evidence.54-57

In the ligands bands at 1460-1500 cm-1

due to the pyridine ring nitrogen remain unchanged on complexation, indicating non

274

involvement of the ring nitrogen in complex formation.58-60

The overall infrared

spectral studies suggests that the ligands are tridentate coordinating through amide

oxygen, azomethine nitrogen and phenolic oxygen forming a five membered chelate

ring.

The infrared spectral data of the compounds and their assignments are shown

in Table 7.IV.

275

Table: 7.IV. Infrared spectral band (cm-1

) of hydrazones derived from isonicotinoyl hydrazide and their ruthenium(III)/ iridium(III)

complexes.

Compound ν(OH) ν(NH) ν(C=O) ν(C=N) ν(C-O) ν(N-N) ν(M-N) ν(M-O) ν(M-Cl)

HBINH 3430 3160 1685 1652 1329, 1156 1045 - - -

o-VINH 3428 3150 1680 1655 1329, 1155 1050 - - -

2-HAINH 3429 3155 1670 1642 1308, 1175 1042 - - -

5-CSINH 3425 3140 1651 1640 1325, 1175 1055 - - -

[Ru(HBINH)(H2O)Cl]2 - - - 1635 1328, 1153 1030 485 440 370

[Ru(o-VINH)(H2O)Cl]2 - - - 1625 1334, 1156 1025 480 430 365

[Ru(2-HAINH)(H2O)Cl]2 - - - 1593 1436, 1214 1028 490 440 380

[Ru(5-CSINH)(H2O)Cl]2 - - - 1595 1321, 1165 1026 485 435 350

[Ir(HBINH)(H2O)Cl]2 - - - 1605 1342, 1122 1030 520 445 375

[Ir(o-VINH)(H2O)Cl]2 - - - 1590 1326, 1216 1026 500 440 378

[Ir(2-HAINH)(H2O)Cl]2 - - - 1605 1330, 1142 1028 495 445 360

[Ir(5-CSINH)(H2O)Cl]2 - - - 1610 1336, 1124 1025 520 440 370

276

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

277

PROTON MAGNETIC RESONANCE SPECTRAL STUDIES

The proton magnetic resonance spectra of the ligands and their iridium(III)

complexes were recorded in a DMSO-d6 solution. 1H NMR spectrum of the ligand

shows signal due to OH at ca. δ12.26 ppm. This disappears in the spectra of iridium

complexes indicating deprotonation and that phenolic oxygen is involved in

complexation.61

A singlet at ca. δ10.50 ppm in the free ligand due to NH disappears in

the complexes and a signal at ca. δ8.68 ppm observed in the spectrum of the free

ligand had shifted to ca. δ8.82 ppm indicating coordination through azomethine

nitrogen. This downward shift may be due to the reduction of electron density at the

azomethine C-H. The methoxy protons of the ligand and complexes appear at ca.

δ3.80-3.92 ppm. The aromatic protons appear as multiplets at ca. δ7.18-7.86 ppm

(isonicotinic 4H). A sharp singlet at δ2.34-2.51 ppm due to the methyl protons

attached to azomethine of the ligands undergoes a downfield shifts due to the

coordination of the azomethine nitrogen.

The Proton magnetic resonance spectral data (δ, ppm) of the ligands and their

iridium(III) complexes are summarised in Table 5.V.

278

Table: 7.V. Proton magnetic resonance spectral data (δ, ppm) of hydrazones derived from isonicotinoyl hydrazide and their iridium(III)

complexes.

Compounds δ(OH) δ(NH) δ(CH=N) δ(Ar C-H) δ(OCH3)

HBINH 12.24 10.50 (s) 7.80 6.68–7.30 (m) -

o-VINH 12.26 10.25 (s) 7.62 6.70–7.20 (m) 3.66

2-HAINH 12.27 10.40 (s) 7.54 6.76–7.24 (m) -

5-CSINH 12.26 10.55 (s) 7.25 6.74–7.14 (m) -

[Ir(HBINH)(H2O)Cl]2 - - 8.20 6.72–7.80 (m) -

[Ir(o-VINH)(H2O)Cl]2 - - 8.12 6.85–7.36 (m) 3.68

[Ir(2-HAINH)(H2O)Cl]2 - - 8.20 6.87–7.30 (m) -

[Ir(5-CSINH)(H2O)Cl]2 - - 8.25 6.80–7.25 (m) -

279

Where,

HBINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxybenzaldehyde

o-VINH = Hydrazone derived from isonicotinoyl hydrazide and o-vanillin

2-HAINH = Hydrazone derived from isonicotinoyl hydrazide and 2-hydroxyacetophenone

5-CSINH = Hydrazone derived from isonicotinoyl hydrazide and 5-chlorosalicylaldehyde

280

THERMAL STUDIES

Thermal analyses of the complexes were studied under dynamic air

atmosphere. Dynamic TG data with the percent weight loss at different steps and their

probable assignments are observed here. The reaction of the ligands HBINH, o-

VINH, 2-HAINH and 5-CSINH with ruthenium(III) and iridium(III) afforded

complexes [Ru(HBINH)(H2O)Cl]2, [Ru(o-VINH)(H2O)Cl]2, [Ru(2-

HAINH)(H2O)Cl]2, [Ru(5-CSINH)(H2O)Cl]2 and [Ir(HBINH)(H2O)Cl]2, [Ir(o-

VINH)(H2O)Cl]2, [Ir(2-HAINH)(H2O)Cl]2, [Ir(5-CSINH)(H2O)Cl]2 respectively. The

T G studies were done for the complexes where the complexes show a weight loss of

3.5-3.8% in the temperature range 170-230˚C attributed to two water molecules. A

weight loss of 7.5-7.8% shown by the complexes in the temperature range 270-340˚C

was attributed to elimination of two Cl-. The TG curves were studied in the 30-700˚C

range and showed that the thermal decomposition of the complexes takes place in

several steps. It is possible that different group in the ligands leads to a decrease in the

stability of all the complexes. Furthermore, it is known that the electronegativity and

the atomic radius of the central metal atom also affect the thermal stability. The metal

content in the residue was calculated and found to be consistent with the elemental

analyses of the complexes. On increasing temperature the decomposition continues

with gradual mass loss and stops at 620-670˚C with the formation of Ru2O3 and Ir2O3.

On the basis of above studies following structure has been proposed for the

ruthenium(III) and iridium(III) complexes.

281

N

C

N N

O

M

OH2

Cl

O

O

N

C

NN

O

M

Y

Cl

C

X

OH2

Z

Y

Z

C

X

M = Ru(III), Ir(III)

Fig. 2: The proposed structure of complex

CONCLUSIONS

The new series of novel isonicotinoyl hydrazone derived from

ruthenium(III) and iridium(III) complexes have been reported. The analytical and

physicochemical data of these complexes supported them to be of dinuclear in

character and octahedral environment around the metal ions. Electrical conductance has

described the non-electrolytic behaviour of complexes. Based on various

physicochemical investigations, the ligands are di basic tridentate coordinating through

ONO.

282

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286

CHAPTER 8

Recent years have witnessed a great deal of interest in the synthesis and

characterization of transition metal complexes containing Schiff bases as ligands,1,2

it

play an important role in the development of coordination chemistry as they form

stable complexes with most transition metals which may have importance as

catalysts3,4

for many reactions such as hydrogenation, oxidation, polymerization,

isomerisation. In bioinorganic chemistry, interest in Schiff base complexes has

centered on the role such complexes may play in providing synthetic models for the

metal-containing sites in metallo-proteins and enzymes.5 The growing interest of the

chemists in the study of ruthenium(III) complexes is due to interesting properties.

Change in coordination environment around ruthenium(III) play an important role in

modulating the properties of the complexes. It is an important class of ligands based

on their potential use as ligands at a metal center, their complexing ability containing

different donor atom is widely reported.6,7

The chemistry of transition metal

complexes containing heterocyclic thione donor continues to be of interest on account

of their interesting structural features and also because of their biological

importance.8-10

The combination of the exocyclic thione group and the heterocyclic

molecule, which may contain nitrogen, oxygen or sulphur or a combination of

generates a group of molecules with considerable coordination potential.11-17

The chemistry of transition metal complexes containing heterocyclic thione

donor such as amine and thione substituted triazole continue to be of interest on

account of their interesting structure features and also because of their biological

importance. The presence of an exocyclic thione group along with heterocyclic

molecule make them more interesting because the combination of these two groups

generate a group molecule with considerable coordination potential.

287

Bonding through amine and thione substituents could result in formation of

stable metal complexes involving highly favoured five membered ring system. The

stimulus for the research into the coordination chemistry of heterocyclic thione

donors18

viz., in analytical chemistry; in metal finishing and electroplating industries;

used as polyolefin stabilizers and as accelerators. Fungicidal, insecticidal and

acaricidal activities have also been reported.19-24

Other biological applications include

thyrotoxic activites, central nervous system depressant and platinum pyridine thione

complex has been reported for clinical use in cancer treatment. There is an enormous

amount of information about the quest for synthetic models which compare more or

less successfully with biological compounds.25-32

On the other hand, a great deal of

information regarding the properties of synthetic Schiff bases of potential biological

interest has arisen during the last few years.33-36

Several of these compounds were

characterized and used as models for a series of systems.37-49

The use of these

compounds in catalytic reactions has also been considered.50-56

Literature survey

reveals that a number of complexes with these ligands have been reported for a

variety of transition metals which have shown interesting biological and magnetic

properties.57-60

To extend the knowledge with respect to the coordination and

biological properties of the transition metal complexes of substituted

mercaptotriazoles, we describe here the synthesis and characterization of a series of

ruthenium(III) complexes with Schiff bases derived from substituted mercaptotrizoles

and thiophene-2-carboxaldehyde or pyridine-2-carboxaldehyde.

In this chapter, the synthesis and structural studies of ruthenium(III)

complexes with Schiff bases derived from substituted mercaptotriazoles are described.

288

N

N

N

N

SH

CH

R

N

N

NH

N

CH

R

X X

S

(Thiol form) (Thione form)

X R LH

4-OCH3

S

ATMTH (L1H)

4-OCH3

N

APMTH(L2H)

2-OH

S

STMTH(L1H)

2-OH

N

SPMTH(L2H)

2-Cl

S

CTMTH(L1H)

2-Cl

N

CPMTH(L2 H)

Fig.1: Structure of ligands

289

8.1. EXPERIMENTAL

The syntheses of the ligands are given in chapter 3.

(i) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of 4-methoxy benzoic acid with thiophene-2-

carboxaldehyde (ATMTH) in 1:2 ratio.

An ethanolic solution (25 ml) of ATMTH (0.150 g, 0.001 mol) was added 2

ml saturated solution of KOH. The colour of the solution instant changed. Then added

ethanolic solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol). An instant

change in colour dark brown from orange, dark brown precipitate appeared; the

reaction mixture was refluxed with constant stirring for about 7 hours. The progress of

the reaction was monitored by silica gel TLC. As reaction completes 1/4th

ethanol was

removed by evaporation then product was cooled 1 hour in ice in order to get clear

precipitation and better yield. It was filtered and washed with distil water and dried in

vacuum over fused calcium chloride in order to get desired compound. Yield = 66%

(ii) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of 4-methoxy benzoic acid with pydridine-2-

carboxaldehyde (APMTH) in 1:2 ratio.

An ethanolic solution (25 ml) of APMTH (0.155 g, 0.001 mol) was added 2

ml saturated solution of KOH. The colour of the solution changed. Then added

ethanolic solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol,). An instant

change in colour reddish brown from brown, black precipitate appeared; the reaction

mixture was refluxed with constant stirring for about 8 hours. As reaction completes

1/4th

ethanol was removed by evaporation then product was cooled 1 hour in ice in

290

order to get clear precipitation and better yield. It was filtered and washed with distil

water and dried in vacuum over fused calcium chloride in order to get desired

compound. Yield = 68%

(iii) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of salicylic acid with thiophene-2-carboxaldehyde

(STMTH) in 1:2 ratio.

An ethanolic solution (25 ml) of STMTH (0.151 g, 0.001 mol) was added 2

ml saturated solution of KOH. The colour of the solution changed. Then added

ethanolic solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol). An instant

change in colour black from brown, dark brown precipitate appeared; the reaction

mixture was refluxed with constant stirring for about 8 hours. The progress of the

reaction was monitored by silica gel TLC. After 1 hour the colour of reaction mixture

turned black. As reaction completes the solvent evaporated and reduced 1/4th

ethanol

was removed by evaporation then product was cooled 1 hour in ice in order to get

clear precipitation and better yield. It was filtered and washed with distil water and

dried in vacuum over fused calcium chloride in order to get desired compounds. Yield

= 56%

(iv) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of salicylic acid with pydridine-2-carboxaldehyde

(SPMTH) in 1:2 ratio.

An ethanolic solution (25 ml) of SPMTH (0.148 g, 0.001 mol) was added 2

ml saturated solution of KOH. The colour of solution changed. Then added ethanolic

solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol). An instant change in

colour black from brown, mud green precipitate appeared; the reaction mixture was

291

refluxed with constant stirring for about 8 hours. The progress of the reaction was

monitored by silica gel TLC. After 1 hour the colour of reaction mixture turned green.

As reaction completes the solvent evaporated and reduced 1/4th

ethanol was removed

by evaporation then product was cooled 1 hour in ice in order to get clear

precipitation and better yield. It was filtered and washed with distil water and dried in

vacuum over fused calcium chloride in order to get desired compound. Yield = 59%

(v) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of 2-chlorobenzoic acid with thiophene-2-carboxaldehyde

(CTMTH) in 1:2 ratio.

Freshly prepared an ethanolic solution (25 ml) of CTMTH (0.144 g, 0.001

mol) of ligand was taken in round bottom flask and heated, added 2 ml saturated

solution of KOH. The colour of ligand solution change and clear solution obtained.

Then added ethanolic solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol)

in ligand solution. An instant change in colour brown from black, brown precipitate

appeared; the reaction mixture was refluxed with constant stirring for about 7 hours.

After reaction completes 1/4th

ethanol was removed by evaporation then product was

cooled for 2 hour on crushed ice in order to get clear precipitation and better yield. It

was filtered and washed with distil water and dried in vacuum over fused calcium

chloride in order to get desired compound. Yield = 60%

(vi) Synthesis of Ruthenium(III) complex with Schiff base derived from

mercaptotriazole of 2-chlorobenzoic acid with pydridine-2-carboxaldehyde

(CPMTH) in 1:2 ratio.

Freshly prepared an ethanolic solution (25 ml) of CPMTH (0.157 g, 0.001

mol) of ligand was taken in round bottom flask and heated, added 2 ml saturated

292

solution of KOH. The colour of ligand solution change and clear solution obtained.

Then added ethanolic solution (10 ml) of ruthenium(III) chloride (0.065 g, 0.001 mol)

in ligand solution. An instant change in colour black from reddish brown, black

precipitate appeared; the reaction mixture was refluxed with constant stirring for

about 8 hours. After reaction completes 1/4th

ethanol was removed by evaporation

then product was cooled for 2 hour on crushed ice in order to get clear precipitation

and better yield. It was filtered and washed with distil water and dried in vacuum over

fused calcium chloride in order to get desired compound. Yield = 67%

All the reactions and analytical data are summarized in Table 8.I and Table

8.II.

293

Table: 8.I. Reactions of ruthenium(III) chloride with Schiff bases derived from substituted mercaptotriazole.

Reactants Molar ratio Stirring/Refluxing

time (hrs)

Product Colour Decomp.

Temp.

Yield (%)

RuCl3∙3H2O + ATMTH 1:2 7 [Ru(ATMT)2(H2O)2]Cl Dark brown 275 66

RuCl3∙3H2O + APMTH 1:2 8 [Ru(APMT)2]Cl Black 280 68

RuCl3∙3H2O + STMTH 1:2 8 [Ru(STMT)2(H2O)2]Cl Black 272 58

RuCl3∙3H2O + SPMTH 1:2 8 [Ru(SPMT)2] Cl Mud green 278 59

RuCl3∙3H2O + CTMTH 1:2 7 [Ru(CTMT)2(H2O)2] Cl Brown 280 60

RuCl3∙3H2O + CPMTH 1:2 8 [Ru(CPMT)2] Cl Black 265 67

294

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

295

Table: 8.II. Analytical data of ruthenium(III) complexes with Schiff bases derived from substituted mercaptotriazoles.

Complexes M.Wt.

Found

(Calcd.)

Analysis found (calcd.)%

C H N S Cl Ru

[Ru(ATMT)2(H2O)2]Cl 803

(803.4)

42.32

(43.83)

3.85

(3.94)

7.15

(7.30)

8.15

(8.35)

4.42

(4.62)

12.70

(13.17)

[Ru(APMT)2]Cl 758

(758.4)

45.08

(47.97)

3.90

(4.02)

10.20

(11.77)

6.26

(6.74)

3.15

(3.72)

10.42

(10.62)

[Ru(STMT)2(H2O)2]Cl 775

(775.3)

43.80

(44.16)

3.55

(3.70)

7.20

(7.92)

8.80

(9.06)

4.55

(5.01)

13.66

(14.29)

[Ru(SPMT)2]Cl 730

(730.4)

46.82

(48.50)

3.60

(3.84)

11.88

(12.57)

6.60

(7.19)

3.95

(3.97)

10.72

(11.33)

[Ru(CTMT)2(H2O)2]Cl 812

( 812.2)

48.25

(50.58)

3.38

(3.74)

6.88

(6.94)

7.55

(7.94)

3.85

(4.39)

11.26

(12.51)

296

[Ru(CPMT)2]Cl 767

(767.3)

52.90

(53.41)

3.45

(3.66)

10.26

(11.32)

6.40

(6.48)

3.42

(3.58)

10.12

(10.25)

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

297

8.2. RESULT AND DISCUSSION

A Systematic study of the reactions of ruthenium(III) chloride with

monobasic Schiff bases (L1H and L2H) in molar ratio 1:2 respectively. The ligands

formed by condensation of substituted various acids i.e. 4-methoxybenzoicacid,

salicylicacid, 2-chlorobenzoicacid; forming Schiff bases of substituted

mercaptotriazole with thiophene-2-carboxaldehyde or pyridine-2-carboxaldehyde in

ethanolic medium exhibits complexes of the type [Ru(L1)2(H2O)2]Cl and [Ru(L2)2]Cl.

The reaction can be represented by the following equations:

RuCl3∙3H2O + 2L1H EtOH

[Ru(L1)2(H2O)2]Cl + 2HCl

L1H = ATMTH; STMTH; CTMTH

RuCl3∙3H2O + 2L2H EtOH

[Ru(L2)2]Cl + 2HCl

L2H = APMTH; SPMTH; CPMTH

The analytical and physical data of the ligands and the complexes are in

agreement with their molecular formulae. Complexes are non-hygroscopic

microcrystalline salts. All these complexes are coloured having a template methods

which exhibit cyclization through ligands. As mercaptotriazole are potentially active

exhibit tautomeric systems. The coloured microcrystalline powders, quite stable in air

and are soluble in dimethylformamide (DMF), tetrahydrofuran (THF),

dimethylsulphoxide (DMSO), but found insoluble in ethanol, methanol, ether, acetone,

CHCl3 and water. All complexes were obtained in good yield and are stable in both

solid and solution phase. The molar conductivities of complexes in DMF (10-3

M)

solution exhibit 1:1 electrolytic nature.

298

MAGNETIC MOMENT

Magnetic moment measurements provide information regarding the structure

of the complexes. The room temperature magnetic moments show that the complexes

are one electron paramagnetic, in the range 1.69-1.82 B.M; lower than the predicted

normal values (2.10 B. M.) Table 8.III corresponding to +3 ruthenium, suggesting a

low spin 4d5, S = 1/2 configuration around octahedral ruthenium(III) with t2g

5

configuration.61

These low values may be indicative of the presence of lower symmetry

ligand field and the formation of molecular orbital by the extended overlap of the metal

and ligand orbitals.62

Progressive quenching of the orbital angular momentum by spin

orbit coupling that removes the degeneracy of the triplet ground term cause lowering of

the magnetic moment.63

Thus, extensive spin orbit coupling can reduce the magnetic

moment below that of the spin only value.

ELECTRONIC SPECTRAL STUDIES

The electronic absorption spectra of ruthenium(III) complexes have been

recorded in dimethylsulphoxide and the bands obtained and their corresponding

assignments are given in Table 8.III. The majority of the complexes exhibit d-d

transition typically observed for octahedral ruthenium in the +3 oxidation state. The

ruthenium(III) complexes showed bands which are observed lie in visible region in the

range of 13500-13890 cm-1

, 17440-18223 cm-1

and 23200-23800 cm-1

assigned as64,65

2T2g →

4T1g (ν1),

2T2g →

4T2g (ν2) and

2T2g →

2A2g,

2T1g (ν3). The low intensity of these

transitions suggested that they appear to be characteristic of the ruthenium(III)66,67

complexes. The two low intensity broad bands are assigned to spin forbidden transitions

while remaining bands in range 23200-23800 cm-1

are assigned to transitions to doublet

states. High crystal field stabilization renders all ruthenium(III) complexes low spin

299

Table: 8.III. Magnetic moment and electronic spectral data of ruthenium(III) complexes with Schiff bases derived from substituted

mercaptotriazoles.

Complexes λmax (cm-1

) Assignments µeff (B.M.)

[Ru(ATMT)2(H2O)2]Cl 13500

17440

23800

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.70

[Ru(APMT)2]Cl 13800

18000

23600

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.75

[Ru(STMT)2(H2O)2]Cl 13900

17480

23460

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.75

[Ru(SPMT)2]Cl 13720

17985

23000

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.80

300

[Ru(CTMT)2(H2O)2]Cl 13890

18000

23750

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.82

[Ru(CPMT)2]Cl 13900

18223

23200

2T2g →

4T1g

2T2g→

4T2g

2T2g→

2A2g,

2T1g

1.69

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

301

with one electron as d5

system corresponding to the t2g5

configuration. The strong field

electrostatic matrices of Tanabe and Sugano68

predict eight transitions from the (t2g5,

eg0) ground state to the (t2g

4eg

1) doublet state configuration and two transitions from the

ground state to the t2g4eg

1 quartet states. These d-d transition may be expected from the

2T2g ground state and occur in increasing order of energy. However many low energy

charge transfer bands of L (π) → metal (t2g) types are also possible. This is in

conformity with other ruthenium(III) octahedral complexes.69,70

INFRARED SPECTRAL STUDIES

The diagnostic infrared bands of the ligands and their respective ruthenium(III)

complexes gave positive indications with regard to the bonding. The ligand molecules

used in the present study are capable of exhibiting thione thiol tautomerism. In the

spectra of the free ligands the presence of bands at 3060-3210 cm-1

and 2440-2560 cm-1

due to ν(N-H) and ν(S-H) respectively,71

clearly give an evidence of establishment of

this type of thione thiol tautomeric system. The ligand molecules contain a

thioamide moiety H-N-C=S or N=C-SH and hence give rise four thioamide

characteristic bands in the region 1530-1550, 1350-1395, 978-1042 and 750-820 cm-1

which assigned as thioamide-I, II, III and IV bands, respectively. These bands are not

pure and have contributions from δ(C-H)+δ(N-H), ν(C=S)+ν(C=N)+δ(C-H), ν(C-

N)+ν(C=S) and ν(C=S) vibration modes respectively. It has been suggested that the

coordination of the amide nitrogen is accompanied by a small increase in the thioamide-

I band while coordination via sulphur atom causes the decrease in the frequency of the

thioamide-IV band.72

In the spectra of complexes, however, all the thioamide bands

disappeared indicating that the mixing of ν(C-N), δ(N-H) and ν(C=S) vibrations may be

absent. The deprotonation of thiol group and complexation through sulphur atom is

indicated by absence of the band at 2440-2560cm-1

(due to ν(S-H) in the spectra of

302

complexes. In the spectra of complexes appearance of a new band at 650-700 cm-1

due

to conversion of C=S into C-S further supported the coordination through sulphur atom.

The ν(M-S) vibration appear at 365-380 cm-1

in the spectra of complexes.73

The band at

1600-1625 cm-1

corresponding to azomethine ν(C=N) of free ligands, shifts to lower

wave numbers on complex formation by 15-20 cm-1

hence, the nitrogen atom of the

azomethine group is coordinating to metal ion in all complexes. This coordination mode

was further confirmed by the presence of a band at 470-490 cm-1

in complexes assigned

to ν(M-N) vibrations.74

This indicated involvement of the azomethine linkage in

coordination.75-77

The spectra of the ligands STMTH and SPMTH show bands at ca.

3400 cm-1

due to ν(O-H). In the parent complexes these bands persist indicating the non

coordination of phenolic oxygen to metal. As additional evidence in complexes derived

from L1H band in range 520-540 cm-1

assigned to ν(M-O) of coordination water

molecule to metal ion. In the spectrum of ligand (L2H) due to the pyridine ring vibration

is also appeared at ca. 1476 cm-1

and ca. 1442 cm-1

. In the spectra of complexes the

band shifted is shifted to lower wave number side indicating coordination through

nitrogen of the pyridine ring. The band corresponding to the coordinated pyridine ring is

also observed in the region 240-260 cm-1

in the ruthenium(III) complexes derived from

ligand (L2H).

The bands corresponding to ligands and complexes are summarized in Table

8.IV.

303

Table: 8.IV. Infrared spectral bands (cm-1

) of the Schiff bases derived from substituted mercaptotriazoles and their ruthenium(III)

complexes.

Compound ν(O-H) ν(N-H) ν(C=N) ν(S-H) ν(Ru-N) ν(Ru-O) ν(Ru-S)

ATMTH - 3210 1618 2455 - - -

APMTH - 3060 1613 2485 - - -

STMTH 3405 3085 1615 2440 - - -

SPMTH 3410 3087 1605 2560 - - -

CTMTH - 3095 1625 2502 - - -

CPMTH - 3190 1614 2490 - - -

[Ru(ATMT)2(H2O)2]Cl - - 1597 - 490 530 375

[Ru(APMT)2]Cl - - 1600 - 485 - 378

[Ru(STMT)2(H2O)2]Cl 3405 - 1605 - 470 520 365

[Ru(SPMT)2]Cl 3410 - 1595 - 490 - 369

[Ru(CTMT)2( H2O)2]Cl - - 1600 - 480 540 380

[Ru(CPMT)2]Cl - - 1595 - 482 - 372

304

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

305

PROTON MAGNETIC RESONANCE SPECTRAL STUDIES

The proton magnetic resonance spectra of the ligands have been recorded in

deuterated dimethylsulphoxide. The following conclusions can be derived by the

spectra of the Schiff base ligands.

(i) The spectra of all the ligands show a band due to –SH proton appears as singlet at ca.

δ8.60 ppm, indicating that the ligand exhibit in thiol form.

(ii) The singlet at δ8.14-8.34 ppm in the spectra of ligands is ascribed to azomethine

protons.

(iii) In the spectra of the ligands APMTH, SPMTH and CPMTH a multiplet was

observed at δ7.60-7.76 ppm. It include probably for both the aromatic protons of the

phenyl and pyridine ring.

(iv) For ligands ATMTH, STMTH and CTMTH three multiplets are observed in the

region δ5.84-6.76 ppm along with multiplets of aromatic protons. This could be due to

thiophene protons.

(v) The other signals appeared in the spectra of ligands at ca. δ3.46 ppm due to –OCH3

group and at ca. δ9.46-9.65 ppm in the spectra of ligands STMT and SPMT may be

assigned to phenolic proton.

Proton magnetic resonance spectral data are summarized in their corresponding

Table 8.V.

306

Table: 8.V. Proton magnetic resonance spectral data (δ, ppm) of the Schiff bases derived from substituted mercaptotriazoles.

Compounds δ(S-H) δ(HC=N) δ(Ar-H) δ(OH) δ(OCH3)

ATMTH 8.56 8.14 (s) 6.68 (m) - 3.46 (s)

APMTH 8.58 8.36 (s) 7.60 (m) - 3.52 (s)

STMTH 8.64 8.28 (s) 5.84 (m) 9.46 -

SPMTH 8.62 8.38 (s) 7.74 (m) 9.65 -

CTMTH 8.46 8.28 (s) 6.76 (m) - -

CPMTH 8.63 8.34 (s) 7.76 (m) - -

Where,

ATMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

APMTH = Schiff base derived from 3-(4-methoxyphenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

STMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

SPMTH = Schiff base derived from 3-salicyl-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

CTMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and thiophene-2-carboxaldehyde

CPMTH = Schiff base derived from 3-(2-chlorophenyl)-4-amino-5-mercapto-1,2,4-triazole and pydridine-2-carboxaldehyde

307

FAB MASS SPECTRAL STUDIES

The spectra of the ligands FAB mass spectra suggested the complete

structure of the compounds. The mass spectral behaviour of the ligands as well as of

their metal complexes is reported here. Their fragmentation revealed the exact

composition of the compounds formed. Mass spectra of the ligands namely ATMTH,

APMTH, STMTH, SPMTH, CTMTH and CPMTH show molecular ion peak at m/z =

316, 311, 302, 297, 288 and 315 which corresponds to their molecular weight.

Complexes of ruthenium(III) with ligands with composition [Ru(L)2(H2O)2]Cl shown

peaks because of fragmentation of coordination water molecule. In

[Ru(CPMT)2(H2O)2]Cl, the molecular ion peak is m/z = 860 respectively. Other

important peaks included fragments of ligands formed whose clear specification could

not be possible. Although these data obtained due to FAB mass serve to substantiate

the formation of compound but they do not enable to elucidate and to understand the

exact structure of the compounds.

THERMAL STUDIES

The thermal behaviour give the formation about the stability of metal chelates

and decide to an extent whether the water molecules are inside or outside the

coordination sphere. The thermal decomposition of all the compounds is continuous.

Thus, in complexes presence of water molecule and chloride ion in the coordination

sphere was confirmed by dynamic TG and DTG data. In the investigating

decomposition involves two step; first step indicates loss of two water molecules at

temperature range 140-240˚C. Second loss observed at 260-300˚C range due to one

chloride ion. The organic moieties such as ligand decompose in gradual manner with

increasing of temperature which confirmed by mass loss of 31.15-31.50% at this stage.

308

Although thermal degradation of organic moiety could not be approximated, thus

complete decomposition of ligand occurred at ~580-600˚C in all the complexes.

Another mole of triazole moiety was lost between 370-500˚C with a mass loss of 62.30-

63.05% on TG curve. At the final step as the end product stable metal oxide as Ru2O3

and even some times RuO2 were found at the temperature 680-720˚C as carbonaceous

matter.

On the basis of above given studies following structures of ruthenium(III)

complexes have been proposed.

N

N

N

NS

CH

X

S

N

N

N

NS

C H

X

S

Ru

H2O

OH2

Cl

+

-

L1H = ATMTH, STMTH, CTMTH

309

N

N

N

NS

CH

XN

N

N

NS

C H

X

RuCl

+

-

N N

L2H = APMTH, SPMTH, CPMTH

Fig.2: Structure of complexes

CONCLUSIONS

The result shows that Schiff bases have a tautomeric structure, which means

that they exist in the solid state in thione thiol forms. Upon coordination they

probably exist only in the thiol form. The ligands behave as monoanionic bidentate/

tridentate and coordinate to ruthenium(III) ions generating complexes of general

formula [Ru(L)2(H2O)2]Cl and [Ru(L)2]Cl. According to results obtained, the geometry

for all the complexes has been assigned octahedral. As new complexes were

synthesized with moderate yield and their corresponding structures were elucidated by

physicochemical techniques.

310

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