3

Introduction

General

In this thesis, coordination chemistry of CuI, Pd

II, Pt

II and Ru

II metal ions has been

investigated with some heterocyclic thioamides. The interaction of heterocyclic

thioamides with transition, post-transition and main group metals has been the focus of

several investigations [1-10]. These thio-ligands are characterized by thione – thiol

tautomerism and contain chemically active -N(H)-C(=S)- -N(H)-C(=S)-N(H)- type

groups. These adopt thione form in solid state (1a), but adopt thiol form (1b) in solution

phase, particularly in nonpolar solvents [5].

4

6NH

S

2

35

1 N SH

Ia Ib

Most heterocyclic thioamides have one replacable proton and function readily as

monoanions, such as pyridine - 2 - thione (pySH), pyrimidine - 2 - thione (pymSH),

while the disubstituted thiones such as 2- thiouracil (tucH2) and 6 - mercaptopurine

(puSH2) may function as monoanions or dianions. These ligands can bind to metal ions

both as neutral and deprotonated species, via a variety of modes, forming monomers,

dimers, oligomers and polymers.

Pyridine-2-thione, pyrimidine-2-thione, 2- thiouracil and 6 - mercaptopurine are

the thio - analogs of purine and pyrimidine nucleobases, and as such have several

biochemical and other applications. These are used as therapeutic agents,

anticarcinogens, fungicides, polyolefin stabilizers in polymers and plastics, vulcanization

accelerators and inhibitors of metallic corrosion [1-6, 11-29]. Thio - ligands play a major

role in detoxification and sequestration of heavy metals such as Hg [11], S, N- chelation

in Mo complexes is relevant to the reduction of nitrogen by nitrogenase etc. [12]. The

4

gold(I) complexes of thiouracil [13, 14] are used in the treatment of rheumatoid arthritis

and also exhibit carcinostatic activity [15].

Background

Here coordination chemistry of pyridine - 2 - thione (pySH, I) with iron (II),

ruthenium (II), osmium (II), nickel(II), palladium (II), platinum (II), copper(I), silver (I)

and mercury (I) is briefly reviewed [30-62], which provided the background to persue

coordination chemistry of heterocyclic thioamides further.

Fe, Ru, Os

The reaction of FeCl3 with pyridine - 2 - thione followed by its reaction with Ph3P

in ethanol and chloroform gave crystals of [FeCl2(η1 - S - pySH)2] 1 [30] instead of the

expected product [FeCl3(pySH)(Ph3P)2]. In this reaction, reduction of Fe+3

to Fe+2

takes

place. The geometry about Fe(II) is distorted tetrahedral and the ligand is coordinating

through S atom, and the free NH group forms intermolecular hydrogen bond with Cl

atoms of adjacent molecules. In the literature, an ionic complex [pySSpyH]+[FeCl4]

- is

also known [31] .

S

Fe

NH

Cl

1

ClS NH

1

N S

The reaction of Ru(PPh3)3Cl2 with pySH (1:2 ratio) in benzene or toluene in the

presence of triethylamine has formed [Ru(η2-N,S-pyS)2(PPh3)2] 2 [32] complex.

Complex has a distorted octahedral structure. Similar reaction of Ru(dppe)2Cl2 with

pySH in the presence of Et3N in benzene did not form the expected product, [Ru(η2 -

N,S- pyS)2(dppe)] 3 [33], but merely formed crystals of [Ru(dppe)2Cl2] 4 [34]. Thus

complex 3 was prepared by replacing PPh3 from complex 2 by dppe in toluene as a

5

solvent. The compounds with dppm, dppp and dppb, [Ru(η2 - N,S- pyS)2(dppm)], [Ru(η

2

- N,S- pyS)2(dppp)] 5 [35] and [Ru(η2 - N,S- pyS)2(dppb)] 6 [36] were prepared similarly

{dppm = 1,1-bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphosphino)ethane,

dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane}.

All these complexes have distorted octahedral geometry with trans S atoms (S-Ru-S bond

angles, 154.7 – 155.9°). Similar complexes of Os and pyridine – 2- thione are: [OsII(η

2 -

N,S- pyS)2(PPh3)2] 7 [37], [OsIII

(η2 - N,S- pyS)2(PPh3)2]PF6 8 [37].

2-3, 5-8

N S_

Ru

S

S

N

NP

Ru

S

S

N

NPh3P

Ph3P

2

P

PP = dppe ,3, dppp, 5, dppb, 6

3, 5-6

Ru

P

P

P

P

Cl

Cl

4

+

Os

S

S

N

NPh3P

Ph3P

7

Os

S

S

N

NPh3P

Ph3P

8

Ni, Pd, Pt

Only a few nickel compounds with pyS- namely, [Et4N][Ni(η

2 -N,S- pyS)3] 9

[38], (NBu4)[Ni(C6H5)2(η2 - N,S- pyS)] 10 [39], [Ni(η

1 - S- pyS)2(bipy)]0.5 bipy 11 [40]

and [Ni(pyOS)2] [41] (pyOS = 1-oxo-pyridine-2-thione). Complex 9 has octahedral

geometry while complexes 10 and 11 have square planar geometry.

6

9 -11

N S_

Ni

N

S

10

-S

Ni

SS

N

N

119

N

NN

NiS

-

N

Palladium(II) acetate with pyridine - 2 - thione formed a N, S-bridged dimer,

[Pd2(η2-N,S- pyS)4] 12 [42] and same can be prepared from PdCl2 and Na

+pyS

- in

CH3CN solvent [43]. Platinum(II) has formed similar dimer, [Pt2(η2 -N,S- pyS)4] 13

[44]. Reaction of 13 with PPh3 in 1 : 2 ratio formed square planar [Pt(η1 - S-

pyS)2(PPh3)2] 14 [44] complex. Other tertiary phosphine derivatives structurally

established are: [PdCl(η2-N,S- pyS)(PPh3)] 15 [45] and [Pt(η

2 -N,S- pyS)(PPh3)2]

+(PF6)

-

16 [46].

N

N

M M

SN

SNN

N

S

S

12, 13

N S_

M = Pd, 12; Pt, 13

PPh3

PPh3

Pt

S

N

16

+

PPh3

Ph3P

Pt

S

S

14

12 -16

PPh3

Cl

Pd

S

N

15

7

The use of diphosphines in place of PPh3 also gave different results. Palladium

(II) chloride complex with dppe and pySH in the presence of sodium hydroxide in

ethanol, formed [Pd(η1 - S- pyS)2(dppe)] 17 [47, 48]. Platinum(IV) chloride with pySH

and dppe (or dppen) in the presence of triethylamine in solvent benzene, also yielded

similar complexes, [Pt(η1 - S- pyS)2(L-L)] (L-L = dppe 18, dppen 19) {dppen = 1,2-

bis(diphenylphosphino)ethylene} [47, 48]. These compounds contain chelating

diphosphines and S - bonded pyS groups with pendant pyridyl groups.

N

N

PP = dppe ,17,18, dppen, 19

N S_

P

P

M

S

S

17 - 19

17 - 19

Some other dinuclear complexes reported are: [{Pd(η2 - N,S- pyS)(PMe3)Cl}2] 20

[49], [{Pt(η2 - N,S- pyS)(en)}2]Cl2 21, 22 [50], [Pt2(en)2(η

2 - N,S- 4-MepyS)2]Cl2. 3H2O

23 [50]. In the Pd dinuclear complex, metal metal distances (2.595 – 2.848 Å) are long

[51].

Pd Pd

SNN S

20

PMe3 PMe3

Cl Cl

Pt Pt

SNN S

21,22

N NN N

ClPt Pt

SN

SNN

N

S

S

Cl

23

8

N N =

N S_

20 - 22

N S_

23

MeEthylene diamine

Cu and Ag

Reaction of CuCl2.2H2O with pySH in ethanol formed Cu(I) complex of

stoichiometry, CuCl(pySH), which on further reaction with two equivalents of Ph3P in

CHCl3 formed the product, [CuCl(η1 - S- pySH)(PPh3)2] 23 [52,53]. It has tetrahedral

geometry with strong NH∙∙∙Cl intramolecular hydrogen bonding. Copper(I) bromide

formed both mononuclear complex, [CuBr(η1-S- pySH)(PPh3)2] 24 as well as a dinuclear

complex, [Cu2(µ-S-pySH)2Br2(PPh3)2] 25 [54].

24

S

Cu

N

ClPh3P

PPh3

23

Cu Cu

S

SPh3P

Br

Br

HN

NH

25

PPh3

23 - 25

NH

S

H........

S

Cu

N

BrPh3P

PPh3

H........

9

Reactions of Copper(I) halides with pySH in the presence of a series of diphosphine

ligands {dppm, dppe, dppp, dppb, dppen} yielded interesting results. Copper(I) chloride

and bromide formed complexes: [CuX(pySH)(L-L)] 26 {X = Cl, Br, L-L = dppe, dppp,

dppb} [55]. For X = Br, L-L = dppe, it was shown to have structure [Cu2Br2(µ-P,P-

dppe)2(pySH)2] 27 [56]. Copper(I) iodide has formed an iodo-bridged hexanuclear Cu(I)

linear polymer, [Cu6(µ3-S- pySH)4(µ2-S- pySH)2(I)4(µ-I)2]n. 2nCH3CN 28 in the presence

of diphosphines (dppm, dppp, dppb, dppen) and with dppe it gave a trinuclear complex,

[Cu3I3(dppe)2(η1 - S- pySH)2] 29 [57].

26

S

Cu

NH

P

P

XHN

NH

Cu Cu

P

S

SBr

Br

27

P

P P

NH

CuCuI

I

P

P

Cu

P

P

P P

IS

NH

Cu

I

S

CuI

Cu

S

Cu

I

S

Cu

I

I

SS

S

Cu

I

28

NH

NH

HN HN

HN

29

10

26 - 29

NH

S

P P = dppe

Reactions of Cu(I) halides with substituted tertiary phosphines, namely, p-tolyl3P

and m-tolyl3P and pySH formed dinuclear complexes, [Cu2X2(µ - S- pySH)2(p-tol3P)2]

(X = Br, 30 [52]; I, 31 [58]), [Cu2Br2(µ - S- pySH)2(m-tol3P)2] 32 [59].

30 - 32

NH

S

Cu Cu

S

Sp-tol3P X

X

HN

NH

30, 31

P(p-tol)3

Cu Cu

S

Sm-tol3P Br

Br

HN

NH

32

P(m-tol)3

Reactions of silver(I) chloride/bromide with PPh3 in acetonitrile and pyridine – 2

– thione in CHCl3 in 1:1:1 ratio have yielded S - bridged dimers of general formula,

[Ag2X2(µ-S-pySH)(PPh3)2] {X = Cl, 33; Br, 34} [60]. The central Ag2S2 cores form

parallelogram with unequal Ag – S bond distances. The geometry is highly distorted

tetrahedral.

11

X = Cl 33, Br 34

Ag Ag

S

SPh3P

X

X

HN

NH

33, 34

PPh3

33, 34

NH

S

Hg

Organomercury(II) with pySH formed a complex, [PhHg(η1- S-pyS)] 31 [61]. In

this complex Hg is strongly bonded to one C and one S atom. This interaction is

relatively weaker than with N and very weak with second S atom of second molecule.

The geometry about Hg atom is distorted T-shaped. Another complex reported in

literature is: [MeHg(η1-S-pyS)] 32 [62]. In this complex, the ligand is unidentate,

bonding via S - donor atom. The geometry of the complex is trigonal bipyramidal,

considering long Hg∙∙∙S interactions with adjacent molecules.

N S_

31 - 32

Hg

N

S

C6H5

Hg

S

SS

N

Me

3231

Survey of literature with pyrimidine – 2 – thione and allied ligands

In this section, a survey of coordination chemistry of ruthenium(II), palladium(II),

platinum(II) and copper(I) with pyrimidine-2-thione (pymSH, II), 2-thiouracil (tucH2,

III), 2,4-dithiouracil (dtucH2, IV) and 6 – mercaptopurine (6-puSH2, V) is described.

12

N

NH

S

pymSH,II

N

N

N

NH

SH

6-puSH2,V dtucH2, IV

NH

NH

tucH2, III

O

NH

NH

S

7

8

9S S1 1 1

1

2 2 2 2

3 3 3

3

4 4 4

4

5 5 5 5

6 6 6

Pyrimidine - 2 - thione can coordinate to a metal ion via different donor atoms.

For example, neutral pyrimidine - 2 - thione shows S - bonding [VIa], while, anionic

pymS–

exhibits 1- S- bonding [VIb], N, S - chelation [VIc], N, S- bridging [VId], N, S-

chelation-cum-S-bridging [VIe], as well as N, S-bridging-cum-S-bridging [VIf]. Neutral

thiouracil shows S - bonding similar to VIa, while deprotonated tucH– shows S –

bonding, N, S- chelation and N, S- bridging similar to VIb, VIc and VId respectively.

Finally, neutral 6-mercaptopurine shows S - bonding similar to VIg, deprotonated puS–2

exhibits S - bonding and N, S- chelation similar to VIh and VIi respectively.

S

M M

S

MM

VIa VIb VIc

VId VIe

M

VIf

M

M

NH

N

N

N

SN

N

SN

N

M

SN

N

MM

SN

N

13

HN

N

N

NH

S

M

N

N

N

N

S

M

N

N

N

N

SM

VIg VIhVIi

The work is described under different sub-heads as follows:

Mo, W

Pyrimidine-2-thione and its derivatives have formed various types of complexes

with molybdenum [63-70] and tungsten [71-74]. A few examples are cited below:

[MoI(CO)3(η

2-N,S-dmpymS)] 33 [63], [Mo

IVO2(η

2-N,S-pymS)2] 34 [64], dimers

[Mo2II(η

2-N,S-dmpymS)4]2 35 [67] and [Mo

IIIO2(η

2-N,S-pymS)(py)]2 36 [68]. Complexes

are having N, S- chelation and N, S-bridging by the ligands. There is only one 2-

thiouracil complex, [MoII(Cp)2(η

2-N,S-tucH)](PF6) 37 [70].

Mo

S

NOC

CO

OC

33

Mo

N

S

N

S

O

O

34

Mo Mo

S

SN

N

NN

S

S

35

Mo

O

O

MoS

N

SN

pypy

O O 34, 3633, 35

36

N

N

CH3

H3C S_

N

N S_

14

Mo

N

S

37

NH

N

O

_S

37

+

Tungsten complexes are in 0, II and IV oxidation states. Pyrimidine - 2 - thione

formed, [Et4N][W(CO)4(η2-N,S-pymS)] 38 [71] and [W

II(CO)3(η

2-N,S-pymS)2] 39

complexes [72]. The anion of 38 has distorted octahedral structure, while 39 has

monocapped trigonal prism structure. With 2-thiouracil tungsten formed both distorted

tetrahedral, [WIV

(Cp)2(η2-N,S-tucH)]PF6 40 [70], and octahedral [Et4N][W

0(CO)5(η

1-S-

tucH)] 41, complexes [74].

Mn, Re

There is only one manganese complex, [MnII(η

2-N,S-dmpymS)2(phen)] 42 [75]

with a substituted pyrimidine - 2 - thione known so far.

N

N S_

-

38,39

W

N

S

N

S

COOC

CO

W

N

SOC

CO

CO

OC

3839

NH

N

O

_S

40,41

W

NS

OC

CO

CO

OC

CO

-

W

N

S

40

+

41

15

MnN

N

S

S

N

N

4242

N

N

CH3

H3C S_

Rhenium complexes with pyrimidine - 2 - thione and its derivatives [76-82], has

formed, mononuclear octahedral, [ReIII

Cl2(PPh3)2(η2-N,S-dmpymS)] 43 [76],

[ReIV

OCl2(PPh3)(η2-N,S-dmpymS)] 44 [76], and [Re

IVO(η

1-S-pymSH)(η

2-N,S-pymS)2]

45 [78], a distorted pentagonal bipyramidal, [ReIII

(PPh3)(η2-N,S-pymS)3] 46 [78] and

dinuclear [Re2(CO)8(µ-H)(µ-S-pymS)] 47 [80] and [(Re2O2(η2-N,S-dmpymS)4)O] 48

[81] complexes. In 47, two Re atoms are bridged through S of pymS- and H

- ion. In 48,

two Re atoms are bridged through O atom and the ligand is N, S- chelated. Only one

dinuclear complex of rhenium with uninegative 6-mercaptopurine, namely, [(Re2O2(η2-

N,S-puS)4O] 49 [83] is known so far. In this complex, two Re atoms are bridged

through O and the ligand is N, S- chelated.

PPh3Ph3P

Cl

Cl

Re

N

S

O

43 44

Ph3P

Cl

Cl

Re

N

S

S

HN

N

45

O

ReS

NS

16

S

N

Re

N

SN

S

46

Ph3PRe Re

S

H

N

CO

COCO

CO

CO

CO

OC

OC

47

O

ReSN

S N

O

ReSN

S N

O

48

O

ReSN

S N

O

ReSN

S N

O

49

N

N S_

45 -4743, 44, 48

N

N

CH3

H3C S_

49

N

N

N

NH

S-

Ru, Os

A number of mono- and tri- nuclear ruthenium complexes with pyrimidine - 2 -

thione and its derivatives have been updated [84-89]. A few examples are [Ru(bipy)2(η2-

N,S-pymS)](ClO4) 50 [84], [Ru(PPh3)2(η2-N,S-pymS)2]Cl2 2H3O

+ 51 [85], [Ru3(CO)9(µ-

S,N-dmpymS)H] 52 [86], [Ru3(CO)10(µ-S-dmpymS)2] 53 [86], [Ru3(CO)9(η1-S-

pymS)H] 54 [87]. In 50 and 51, octahedral complexes, the ligand is N, S- chelated, and

in trinuclear cluster 53, two Ru atoms are bridged through the S atom. In 52, 54, the

thioligands exhibit µ - S,N – bridging.

6-Mercaptopurine has formed octahedral complexes with ruthenium, viz.,

[Ru(bipy)2(η2-N,S-puSH2)]Cl2 55 [90] and [Ru(PPh3)2(η

2-N,S-puSH2)2](ClO4)2 56

17

[91].The oxidation state of ruthenium is II and the ligand is coordinated as neutral,

showing N, S- chelation.

+

NN

50

N

Ru

S

NN

PPh3

RuSN

S N

PPh3

51

2+

H

Ru

Ru RuS

COCO

CO

CO

CO

OC

OC

OC

OCN

52, 54

Ru

Ru Ru

S

COCO

CO

CO

CO

OC

OC

OC

OC CO

S

NN

53

Ru

S

S

N

N

2+

Ph3P

Ph3P

56

NN

N

RuS

NN

2+

55

18

N

N S_

50, 51, 54

52, 53

N

N

CH3

H3C S_

55,56

HN

N

N

NH

S

Only trinuclear osmium complexes with pyrimidine- 2- thione and its derivatives

have been reported, namely, [Os3(CO)9(µ-N,S-dmpymS)(µ-S-dmpymS)] 57 [92],

[Os3(CO)10(µ-S-dmpymS)2] 58 [92] and [Os3(CO)10(µ-S-dmpymS)H] 59 [93]. In 57,

dmpymS- shows mixed bonding, while in 58 and 59, it is µ - S - bridging.

S

Os

Os OsS

COCO

CO

CO

CO

OC

OC

OC

OCN

57

N

Os

Os Os

S

COCO

CO

CO

CO

OC

OC

OC

OC CO

S

NN

58

57 -59

N

N

CH3

H3C S_H

59

Os

Os Os

S

COCO

CO

CO

CO

OC

OC

OC

OC CO

N

Co, Rh

Cobalt has formed only octahedral complexes with pyrimidine - 2 - thione and its

derivatives [94-101], some of the examples are: [Co(η2-N,S-dmpymS)3] 60 [94, 95],

19

[Co(η2-N,S-mpymS)(en)2](ClO4)2

61 [96] and [Co(η

2-N,S-apymS)(en)2](ClO4)2 62 [97].

The oxidation state of Co is III and ligands are N, S- chelated in the complexes. The S-

atoms of the ligands are trans to each other in 60. 2-Thiouracil and 2,4-dithiouracil

(dtucH2) have yielded octahedral complexes, [Co(η2-N,S-tuc)(en)2](ClO4).H2O 63 [102]

and [Co(η2-N,S-dtuc)(en)2](ClO4)

64 [103]. The ligand 2-thiouracil and 2,4-dithiouracil

are coordinating as dianions.

Co

S

N

S

S

N

N

6061,62

Co

N

S

H2N

NH2

H2N

NH2

3+

Co

N

S

H2NNH2

H2N

NH2

3+

63,64

61 62

N

N

CH3

S_

H2N-CH2-CH2-NH2NH2H2N =

N

N

NH2

S_

63

N

N

O

_S

N

N

S

_S

64

_ _

60

N

N

CH3

H3C S_

Rhodium has formed mono- and di- nuclear square planar complexes with

pyrimidine - 2 - thione and its derivatives [104-106]. Some of the examples are,

[RhII(cp)(η

2-N,S-dmpymS)(η

1-S-dmpymS)] 65 [104], [Rh

I(CO)(η

2-N,S-

dmpymS)(PPh3)] 66 [105], [RhI(CO)2(η

2-N,S-dmpymS)] 67 [106], [Rh2

III(cp)2(µ

3-S,N-

mpymS)2](PF6)2 68 [106]. In 65, one ligand is bonded to Rh atom in 1- S mode and the

second ligand is in 2

– N, S chelation mode, in 66 and 67, it is N, S- chelated and in

68, the ligand is in µ3-S, N- mode.

6-Mercaptopurine with rhodium has formed octahedral complexes [RhIII

(η2-N,S-

puSH2)2(PPh3)(Ph)]Cl2. H2O 69 [107], and [RhIII

(η2-N,S-puSH2)(Ph)Cl2(SbPh3)] 70

[108] (SbPh3 = triphenyl stibine). The ligand is in N, S- chelation mode.

20

Rh

SS NN

65

PPh3

CO

Rh

N

S

CO

Rh

N

S

CO

66

67

Rh Rh

S

S

N

68

N

2+

2+

Ph

Rh

S

Ph

N

Cl

Cl

Ph3Sb

69 70

PPh3

RhSN

S N

65 - 67

N

N

CH3

H3C S_

68

N

N

CH3

S_

69,70

HN

N

N

NH

S

Ni, Pd and Pt

Pyrimidine - 2 - thione and its derivatives have formed a variety of complexes with

nickel [109-114], palladium [115-122], and platinum [123-127]. A few mono- and di-

nuclear complexes of Ni are: [Ni(η2-N,S-pymS)(bipy)2](SbF6) 71 [109],

[(CH3)3N(CH2Ph)]+[Ni(η

2-N,S-pymS)3]

- 72 [110], [(Ph)4P]

+[Ni(η

2-N,S-pymS)3]

- 73

[111]. The oxidation state of nickel is II and the ligand is showing N, S- chelation in 71 ,

72 and 73.

21

S

Ni

SS

N

N

+

71

72, 73

NN

N

NiS

NN

-

N

71 - 73

N

N S_

Several square planar PdII complexes are listed as follows: [Pd(η

2-N,S-dmpymS)2]

74 [115], [Pd(η1-S-pymSH4)4]Cl2.H2O 75 [116, 117], [Pd(η

2-N,S-pymS)(PPh3)2](ClO4)

76 [118], [Pd(µ-N,S-pymS)(PMe3)Cl]2 77 [119] and [Pd(µ-N,S-mpymS)(PMe3)Cl]2 78

[119] and [Pd2(µ-N,S-pymS)2(L)2] 79 [120] {L= (1-methyl imidazol - 2 – yl) ketone} . In

75, the ligand is neutral S- bonded, while in all other cases, the anionic ligands are N, S-

chelating or bridging.

There is one square planar complex of Pd with thiouracil, namely, [Pd2Cl2(PPh3)3(µ3-

N,N,S-tuc)] 80 [120] and one with 9-benzyl-6-mercaptopurine, [Pd(η2-N,S-bpuS)2] 81

[121]. In 80, the ligand is dinegative and coordinated as tridentate through three sites,

while in 81, the ligand is coordinated as uninegative anionic ligand via N7, S donor

atoms.

.

N

74

74

Pd

S S

N

N

N

CH3

H3C S_

NH

PdS

S S

S NH

HN

HN

NH

NH

S

75

75

2+

22

PPh3

PPh3

Pd

S

N

76

+Cl

Cl

Pd

Pd

N

NS

S

77, 78

L

L

N

N

Pd

Pd

N

N

S

N

79

S

N

N

NN

N

O CH3CH3

=

76, 77, 7978

N

N S_

N

N

CH3

S_

L = PMe3

(1-methyl imidazol - 2- yl) ketone

N N

Platinum(II) has formed square planar complexes, [Pt(η1-S-pymS)(terpy)](ClO4) 82

[123], [Pt(η2-N,S-dmpymS)2] 83 [124]. In octahedral complex, [Pt(η

2-N,S-mpymS)2Cl2]

N

N

PPh3

Pd

Ph3P Cl

Pd

Ph3P

Cl S

O

80

N

N

O

_S

80

_

81

81

NPd

S S

N

N

N

N

N

S-

CH2Ph

23

84 [124], the metal has IV oxidation state. Dinuclear PtIII

complexes are: [Pt2(µ-N,S-

pymS)4(η1-S- pymS)Cl] 85 [125, 126], [Pt2(µ-N,S-pymS)4X2] (X = Cl 86, Br 87, I 88)

[124, 127], and [Pt2(µ-N,S-tucH)4I2] 89 [126]. There are PtIII

- PtIII

bonds in 85-89. The

pyrimidine –2-thione and thiouracil ligand are uninegative and coordinate via N, S donor

atoms.

Pt

S N

N

N

N

PtSS

N N

8283

+

Cl

Cl

Pt

84

SN

S N

SCl NPt Pt

SN

SNN

N

S

S

85 X= Cl(86), Br(87), I(88)

XX Pt Pt

SN

SNN

N

S

S

IPt Pt

SN

SNN

N

S

S

I

89

83

N

N

CH3

H3C S_

N

N

CH3

S_

84

N

N S_

82, 85 - 88

NH

N

O

_ S

89

Cu, Ag and Au

Copper(I) halides, azide and thiocyanate salts have yielded several complexes with

pyrimidine - 2 - thione and its derivatives [128-142]. Some of the examples are:

[CuCl(η1-S-pymSH)(o-tol3P)] 90 [128], [Cu(η

1-S-pymSH4)2Cl] 91 [129], [Cu(η

1-S-

pymSH4)2Br] 92 [130], [CuX(η1-S-pymSH)(PPh3)2] {X = Cl, 93, Br, 94, I, 95} [131-

133], [Cu(η1-S-dmpymSH)(L)(PPh3)2] {L = N3, 96, NCS, 97} [134], [Cu(η

1-S-

pymSH)(dppp)X] {X = Cl, 98, Br, 99} [135], [CuBr(η1-S-pymSH)(L)] {L = o-

C6H4(PPh2)2} 100 [136], [CuCl(µ-S-pymSH)(p-tol3P)]2 101 [137], [Cu2X2(µ-S-

24

pymSH)2(η1-S-pymSH)2]2 (X = Cl, Br, and I, 102) [138], [CuX(µ-P,P-dppen)(η

1-S-

pymSH)]2 {X = Cl, 103, Br, 104, I, 105}[139 – 140]. In all the above complexes, the

ligands are neutral 1-S-bonded and the geometry around metal center is distorted

tetrahedral.

Cu

o-tol3P S

Cl

NH

90

o-tol3P = o-(CH3C6H4)3P

Cu

S S

X

NHHN

X = Cl 91, Br 92

S

Cu

NH

X = Cl 93, Br 94, I 95

XPPh3

PPh3

S

Cu

NH

L

L = N3, 96, SCN, 97

PPh3

PPh3PP = Ph2P(CH2)3PPh2 (dppp)

S

Cu

NH

P

P

X

X = Cl 98, Br 99

100

S

Cu

NH

P

P

Br

P P =PPh2

PPh2Cu Cu

S

Sp-tol3P Cl

Cl

HN

NH

101

P(p-tol)3

25

S

SI

Cu Cu

I

S

S

NHHN

NHHN

102

HN

NH

Cu Cu

S

SX

X

P P

P P

(X = Cl, 103, Br, 104, I, 105)

P P = dppen

NH

NH

S

91, 92

N

NH

S

90, 93-95,99-105

N

NH

CH3

H3C S

96, 97

Attempts to grow crystals of CuCl2(η1-S-tucH2)2 from DMF instead formed a

copper(I) complex, Cu(η1-S-tucH2)2Cl·DMF 106 [143,144]. The geometry around Cu(I)

center is essentially trigonal planar with the 1- S bonded neutral tucH2.

6-Mercaptopurine has yielded [Cu2(η1-Cl)2(µ-Cl)2(η

1-S- puSH3)2] 107, [Cu2(η

1-

Cl)4(µ-S- puSH3)2] 108 [145 - 146] The geometry around each Cu is tetrahedral. In

complex 107, Cl is bridging while in complex 108, ligand is bridging through S.

Cl

HN NH

Cu

SSNH

NH

O

S

106106

26

+HN

N

HN

NH

S

107-108

HN

NH

Cu Cu

Cl

Cl

S

SCl

Cl

107HN

NH

Cu Cu

Cl

Cl

S

S Cl

Cl

108

Both silver(I) [147-153] and gold(I, III) [154-159] have formed a variety of

complexes with pyrimidine - 2 - thione and its derivatives. With silver(I), pyrimidine –2-

thione has formed mononuclear, [Ag(PPh3)2(η1-S-pymS)]NO3 109 [147] and dinuclear,

[Ag2(µ-Br)2(PPh3)2(η1-S-pymSH)2] 110 complexes [148]. Gold(I) has formed mono- or

di- nuclear complexes: [Au(η1-S-pymS)(PPh3)] 111 [154], [Au(η

1-S-dmpymS)(PPh3)]

112 [155], [Au(η1-S-dmpymS)2] 113 [156], [Au(µ-N,S-dmpymS)]2 114 [156], [Au(µ-

N,S-pymS)]2 115 [156], [Au(η1-S-apymS)(PPh3)] 116 [157] and [Au(η

1-S-

apymS)(PEt3)] 117 [157]. The geometry around Au centre is linear.

S

Ag

N

PPh3Ph3P

109

Ag Ag

Br

BrS

S

NH

HN

PPh3

Ph3P

110

27

AuPh3P NS

Au

S

S

N

N

111

AuPh3P NS

112113

Au Au

S

S

N

N

114, 115

AuPh3P NS

116

AuEt3P NS

117

110

N

NH

S

N

N S_

109, 111, 114

112, 113, 115

N

N

CH3

H3C S_

NH2

N

N S_

116,117

Thiouracil and 6-mercaptopurine has formed linear gold(I) complexes [160 -

166], namely, [Au(η1-S-tucH)(PPh3)] 118 [162], [Au(η

1-S-tucH)(PEt3)] 119 [163],

[Au(η1-S-puS)(PPh3)] 120 [163,164] and [Au(η

1-S-puS)(o-tol3P)] 121 [165]. The

ligands are 1-S bonded in all these complexes. Only one square planar complex of

gold(III) with 6-mercaptopurine, viz, [Au(η2-N,S-puS)Cl(L)]Cl 122 {L= N, N-

dimethylammoniummethylphenyl}[166] is reported.

28

NH

N

O

S

118,119

AuPh3P NS

118

AuEt3P NS

119

-

AuPh3P NS

120

Auo-tol3P NS

121

AuS

NHN

N

N

NH

S

L

ClCl-

+

120 -122122

-

Zn, Cd and Hg

Pyrimidine - 2 - thione and its derivatives, have formed several complexes with

post - transition elements [167-175]. Complexes of zinc(II) are: [ZnCl2(η1-S-

dmpymSH)2] 123 [167], [Zn(η1-S-mpymSH)4](ClO4)2 124 [168], and [Zn(py)(η

2-N,S-

dmpymS)2] 125 [169] and that of Cd(II) are [Cd(η2-N,S-pymS)2(phen] 126 [173] and

[Cd2(µ3-N,S-pymS-6-CF3)2(η2-N,S-pymS-6-CF3)2] 127 [174]. Complexes 123, 124 have

distorted tetrahedral structures, while complex 125 has square pyramidal structure.

Cadmium complex 126 has octahedral structure, while 127 is a dimer with square

pyramidal geometry around each Cd center.

6- Mercaptopurine and 2 - thiouracil have also formed mono- and di-nuclear complexes

[176 -178], [Cd(η2-N,S-puS)2Cl2] 128 [176] and [Cd(η

2-N,S-puSH2)Cl2(OH2 )]2 129

[177].

29

Cl

S NHCl

123

ZnS NH

2+

124

S NH

ZnS NH

S NH

S NH

Zn

S

NN

S

py

125

S

Cd

N

N

S

126

N

N S

CdCd

N

S

SN

N

N

S

127

Cl

Cl

S

CdNN

S

Cl

CdCd

N

S

ClH2O Cl

N

S

OH2Cl

128 129

124

N

N

CH3

S

123, 125

N

N

CH3

H3C S_

126

N

N S_

127

N

N

CH3

F3C S_

128,129

HN

N

N

NH

S

30

There are several mercury(II) complexes with pyrimidine - 2 - thione and its

derivatives. Some of the examples are, [Hg(Me)(η1-S-pymS)] 130 [178], [Hg(Me)(η

1-S-

mapymS)] 131 [179], [Hg(Me)(η1-S-mpymS)2] 132 [180], [HgI2(η

1-S-pymSH4)] 133

[181], [HgX2(η1-S-pymSH4)2] {X = Cl, 134, Br, 135, I, 136, SCN, 137, CN, 138} [182],

[Hg2Br2(η1-S-pymSH)(PPh3)] 139 [183], [Hg2(µ-Cl)2(η

1-S-pymSH)2(PPh3)2] 140 [184].

In 140, Hg(II) ion is bonded to two P atoms, and two bridging Cl atoms, while the other

Hg(II) ion is bonded to two S- atoms of pyrimidine - 2 - thione ligands and two bridging

Cl atoms.

Hg

N

S

N

N

H3C

H2N S_

CH3

130130-132 131

N

N S_

132

N

N

CH3

S_

X = Cl 134, Br 135, I 136, SCN 137, CN 138

I

N

Hg

S

I

133-138133

134-138

X

SHN

HgS NH

X

NH

NH

S

Br

Br

PPh3

N

NH

SHg

S NH

139

PPh3

PPh3

SN Cl

Hg Hg

ClSN

140139, 140

31

4-Amino-2-thiouracil and 6- mercaptopurine have yielded complexes,

[HgCH3(η1-S-atucH)] 141 [185], and 6-mercaptopurine yielded [HgCl2(η

1-S-puSH2)2],

142 [186].

Hg

N

S

CH3

NH

N

O

_S

141 141

Sn and In

Tin(IV) and indium(III) have formed a few complexes with pyrimidine - 2 - thione

and its derivatives [187-193]. Some of the examples are: [Sn(Ph)3(η2-N,S-pymS)] 143

[187], [Sn(Ph)3(η2-N,S-dmpymS)] 144 [188], [Sn(Ph)2(η

2-N,S-dmpymS)2] 145 [188],

[Sn(Ph)2(η2-N,S-pymS)2], 146 [189], [Sn(CH3)2(η

2-N,S-pymS)2] 147 [190] and [In(η

2-

N,S-pymS)3] 148 [192]. The ligands are N, S-chelating in all these complexes.

Ph

Ph

Ph

N

S

Sn

143, 144

Sn

SN

S

N

Ph

Ph

145

N

S

Ph

Ph

Sn

S

N

146

HN

N

N

NH

S

Cl

Cl

142

Hg

S NH

142

S NH

32

N

SSn

S

N

CH3

CH3

147

S

In

SS

N N

N

148

144, 145

N

N

CH3

H3C S_

143, 146, 147

N

N S_

Background and plan of Work

This survey of literature reveals that coordination chemistry of pyridine-2-thione has

been extensively studied [30-62]. Lobana et al. [33-36,41,43,44,47,48,52,53,55,57,

58,60,61] have investigated coordination chemistry of palladium(II), platinum(II),

ruthenium(II) and copper(I) metal ions with pyridine-2-thione (pySH) as N, S- donor

ligands. Mono- and di- tertiary phosphines such as PPh3, Ph2P(CH2)nPPh2 (n = 1, dppm;

2, dppe; 3, dppp; 4, dppb) were used as co-ligands. Pyridine-2-thione in neutral form

coordinated through S (η1-S and µ-S modes) and as an anionic ligand it either acted as a

N, S- chelating agent, or as a S-donor.

It was intended to extend coordination chemistry of these metals with other

heterocyclic thioamides, namely, pyrimidine-2-thione and purine-6-thione. These latter

ligands have more than two donor atoms and could provide several coordination

possibilities. A survey of literature reveals that only limited coordination chemistry of

pyrimidine-2-thione and purine-6-thione ligands has been reported [84-87, 118, 119],

particularly with the tertiary phosphines as co-ligands.

Keeping the above background in view, it was planned to investigate coordination

chemistry of Ru(II), Pd(II), Pt(II) and Cu(I) using pyrimidine-2-thione and purine-6-

thione ligands.

33

N

NH S

HN

N

N

NH

S

pymSHpuSH2

In detail, it was planned to carry out reactions with the anticipated products as shown

below;

Palladium(II). The starting material PdCl2(PPh3)2 with pymSH and puSH2 could provide

various possibilities (1 – 4, 7 – 10). Likewise with diphosphines as co-ligands, complexes

of the types 5, 6, 11 and 12 were anticipated.

PdCl2(PPh3)2 +N

N S

H

PdCl2(L-L) +N

N S

H

Pd

PPh3S

N

P

P

dppm, dppe, dppp, dppbP P =

PPh3

L-L =

Pd

PPh3S

S PPh3

S N

+

Cl-N

N

Pd

PPh3S

SPh3P

N

NPd

PPh3S

SN N

N

N S_

=

Pd

S

S

N

N

Pd

S

N

+

Cl-P

P

1

2

3

4

56

34

PdCl2(PPh3)2 +

PdCl2(L-L) +

Pd

PPh3S

N

P

P

PPh3

Pd

PPh3S

S PPh3

N

N

Pd

PPh3S

SPh3P

N

N

Pd

PPh3S

SN N

7 - 9, 12

N

N

N

NH

S-

dppm, dppp, dppbP P =L-L =

N

N

N

N

SH

H

Pd

S

S

N

N

Pd

S

N

P

P

9 7

10 8

12 11

S N = N

N

N

N

S-2

10, 11

N

N

N

N

SH

H

Platinum(II). The behaviour similar to that of palladium(II) was anticipated (13 – 24).

N

N S

H

Pt

PPh3S

N PPh3

Pt

PPh3S

S PPh3

N

N

Pt

PPh3S

SPh3P

N

N

Pt

PPh3S

SN N

H2PtCl6 + 2PPh3 +

+

Cl-

13

1416

15

35

P

P

N

N S_

dppm, dppe, dppp, dppbP P =L-L =

Pt

S

S

N

N

Pt

S

N

P

P

S N =

H2PtCl6 + (L-L) +N

N S

H

+

Cl-

1718

P

P

19 - 21, 24

N

N

N

NH

S-

dppm, dppp, dppbP P =L-L =

Pt

S

S

N

N

Pt

S

N

P

P

24 23

S N = N

N

N

N

S-2

22, 23

N

N

N

N

SH

H

H2PtCl6 + (L-L) +

Pt

PPh3S

N PPh3

Pt

PPh3S

S PPh3

N

N

Pt

PPh3S

SPh3P

N

N

Pt

PPh3S

SN N

N

N

N

N

SH

H

2119

2220

H2PtCl6 + 2PPh3 +

36

Ruthenium(II). In case of RuII, complexes of the type 25 – 28 were expected.

RuCl2(PPh3)3 + 2N

N S

H

Et3N

- PPh3

RuCl2(L-L)2 + 2N

N S

H

Et3N

- (L-L)

PPh3

PPh3

S

Ru

P

S

N

N

P

S

Ru

S

N

N

25

26

dppm, dpppP P =L-L =

Ru2Cl3(dppb)3 + 2N

N S

H

Et3N

-2dppb

S

Ru

P

S

N

N

P

Ru(pymS)2(PPh3)2 + dppeEt3N

- PPh3

S

Ru

P

S

N

N

P

27

28

Copper(I). With this metal, complexes of the type 29 – 33 were anticipated.

CuX +N

N S

H

+ PPh3Cu Cu

Ph3P

PPh3

HN

S

X

X

S

NH

N

N S

H

S NH=

Cu

X

PPh3

PPh3

HN S

X = Cl, Br, I

+ 2PPh3

29

30

37

Cu Cu

Ph3P

PPh3

HN

S

X

X

S

NH

CuX ++ PPh3N

N

N

N

SH

H

Cu

X

PPh3

PPh3

HN S

Cu

N

PPh3

PPh3

S

- HX + 2PPh3

S NH N

N

N

NH

S-

N

N

N

N

SH

H

X = Cl, Br, I

=S N

=

25

32

33

29 - 31, 3332

From the above proposed reactions, about 30 complexes have been synthesized

These have been characterized using analytical data, IR spectroscopy, 1H,

13C and

31P

NMR spectroscopy. Eighteen complexes have been studied using single x-ray

crystallography. The details of complexes are described in Chapter 2 and their

experimental details are given in Chapter 3.