LL ee cc tt uu rr ee 88

Complex compounds. Complex compounds. Structure of complex Structure of complex

compounds.compounds.

Associate prof. Associate prof. Yu. B. DmukhalskaYu. B. Dmukhalska

OutlineOutline1.1. Solubility. The mechanism of dissolving.Solubility. The mechanism of dissolving. 2.2. Solubility of gases in liquids. The Henry’s law. Solubility of gases in liquids. The Henry’s law. 3.3. Colligative properties:Colligative properties:a) osmosis. The vant’-Hoff’s law. Hemolysis and plasmolysis;a) osmosis. The vant’-Hoff’s law. Hemolysis and plasmolysis;b) vapor-pressure lowering of solution. A Raoult’s law;b) vapor-pressure lowering of solution. A Raoult’s law;c) boiling-point elevation;c) boiling-point elevation;d) freezing-point depression. d) freezing-point depression.

4. Concept of complex compounds and complexing process.

Nomenclature of complex compounds. Types of complexes.

5. Structure of complex compounds. Isomerism of complex

compounds. Chemical bonds in complex compounds molecule.

6. Stability of complexes and influence of different factors on it.

7. Biological role of complex compounds. Usage of complexing

in chemistry.

Water – Water – main solventmain solventThe water - main component of organisms and The water - main component of organisms and

medium, in which lives the person. The main medium, in which lives the person. The main properties of water that in water can solubility a properties of water that in water can solubility a different matters.different matters.

In the human, animal, plant organisms the water is In the human, animal, plant organisms the water is main part, a constituent solvent and it main part, a constituent solvent and it participates in exchange reactions of matters participates in exchange reactions of matters (hydrolysis, hydration, swelling, digestion). (hydrolysis, hydration, swelling, digestion).

In a human organism are about 70 - 80 % of In a human organism are about 70 - 80 % of water. water.

The mechanism of The mechanism of dissolvingdissolving

(- +)Polar molecule(- +)Polar molecule

((--)) Negative ionNegative ion

(+(+)) Positive ionPositive ion

(-+)(-+)Water dipoleWater dipole

The dissolvingThe dissolving depends primarily on the relative depends primarily on the relative strengths of three attractive forces: strengths of three attractive forces:

1)1) the forces between the particles of the solute the forces between the particles of the solute before it has dissolved before it has dissolved {solute-solute forces),{solute-solute forces),

2)2) the forces between solvent particles before the forces between solvent particles before dissolution has taken place dissolution has taken place ((solvent-solvent solvent-solvent forces),forces),

3)3) the forces that are formed between solute and the forces that are formed between solute and solvent particles during the dissolving process solvent particles during the dissolving process ((solute-solvent forces).solute-solvent forces).

Type of solutionType of solutionAA saturated saturated solution solution is one that is in equilibrium with excess is one that is in equilibrium with excess

undissolved solute,undissolved solute, or would be in equilibrium if excess solute or would be in equilibrium if excess solute were present.were present. The term The term saturatedsaturated denotes the highest denotes the highest concentration of solute which a solution can have and be in concentration of solute which a solution can have and be in equilibrium with any undissolved solute with which it is placed in equilibrium with any undissolved solute with which it is placed in contact.contact.

AnAn unsaturated solution unsaturated solution is one in which the concentration of solute is one in which the concentration of solute is is less thanless than its concentration in a saturated solution. its concentration in a saturated solution.

A A supersaturatedsupersaturated solution is one in which the concentration of solution is one in which the concentration of solute is solute is greater thangreater than its concentration in a saturated solution. its concentration in a saturated solution.

A supersaturated solution is unstable and its solute tends eventually A supersaturated solution is unstable and its solute tends eventually to crystallize out of solution, much as a super cooled liquid tends to crystallize out of solution, much as a super cooled liquid tends eventually to crystallize. eventually to crystallize.

Gas solution Gas solution is not possible to prepare a heterogeneous mixture of two is not possible to prepare a heterogeneous mixture of two gases because all gases mix uniformly with each other in all proportions. gases because all gases mix uniformly with each other in all proportions. Gaseous solutions have the structure that is typical of all gases. Air, the Gaseous solutions have the structure that is typical of all gases. Air, the gaseous solution with which we come in closest contact, is composed gaseous solution with which we come in closest contact, is composed primarily ofprimarily of NN22 (78 % by volume), O (78 % by volume), O22 (21 %), and Ar (1 %), with smaller (21 %), and Ar (1 %), with smaller concentrations of COconcentrations of CO22, H, H22O, Ne, He, and dozens of other substances at very O, Ne, He, and dozens of other substances at very low levels.low levels.

Liquid solutions Liquid solutions have the internal structure that is typical of pure liquids: have the internal structure that is typical of pure liquids: closely spaced particles arranged with little order. Unlike a pure liquid, how closely spaced particles arranged with little order. Unlike a pure liquid, how ever, a liquid solution is composed of different particles. Much of this chapter ever, a liquid solution is composed of different particles. Much of this chapter is devoted to the properties of liquid solutions, and special emphasis is given is devoted to the properties of liquid solutions, and special emphasis is given to to aqueousaqueous solutions, in which the major component is water. solutions, in which the major component is water.

Two kinds of Two kinds of solid solutions solid solutions are common. The first, the are common. The first, the substitutional solid substitutional solid solution,solution, exhibits a crystal lattice that has structural regularity but in which exhibits a crystal lattice that has structural regularity but in which there is a random occupancy of the lattice points by different species.there is a random occupancy of the lattice points by different species.

Disperse systemsDisperse systemsDisperse systems Disperse systems are called are called

systems, which consist of two systems, which consist of two phases, one of which is scattered or phases, one of which is scattered or dispersed in other.dispersed in other.

The disperse phaseThe disperse phase -- phase which is phase which is scattered (dispersed) in mediumscattered (dispersed) in medium..

The disperse medium -The disperse medium - phase in phase in which dispersion donewhich dispersion done. .

Classification disperse Classification disperse systems systems

• By stat of dispersed phase and dispersed medium By stat of dispersed phase and dispersed medium

By size of dispersed phase By size of dispersed phase

Colloidal solutions are Colloidal solutions are disperse systems, which disperse systems, which have have dispersed phase particle, dispersed phase particle, which size between 10which size between 10-9-9 to to 1010-7-7m or 1 nm to 100 nm.m or 1 nm to 100 nm.

Concentration units of solution Concentration units of solution Mass fractionMass fraction ((ii) ) of solute in solution is the ratio of of solute in solution is the ratio of

the mass solute (mthe mass solute (mii) to the mass of solution m) to the mass of solution mii +m +mss; m; mss- - mass of a solvent:mass of a solvent:

Percentage by weight (mass)Percentage by weight (mass) or mass or mass percent,percent, is the is the quantity of one component of a so lution expressed as a quantity of one component of a so lution expressed as a percentage of the total mass:percentage of the total mass:

where where mm - percent by mass, - percent by mass, mmAA, m, mBB, m, mCC - mass of components in the solution. - mass of components in the solution.

Mass concentration, titer (T)Mass concentration, titer (T) is number grams of solute (m) per one milliliter is number grams of solute (m) per one milliliter of solution (V). Or it is the ratio of the quantity grams of solute and volume of solution (V). Or it is the ratio of the quantity grams of solute and volume solution: solution:

T = T = m . m . V V Molarity (CMolarity (CMM), or molar concentration), or molar concentration, is the number of moles of solute , is the number of moles of solute

dissolved per liter of solution. dissolved per liter of solution.

CCMM = = γ γ = = m . m . V MVV MVwhere: where: CCMM - - molarity molarity (by mole of solute per liter of a solution);(by mole of solute per liter of a solution);

γγ - number mole solute; - number mole solute;m - mass solute, grams;m - mass solute, grams;M - molar mass solute, in grams/mole;M - molar mass solute, in grams/mole;V - volume of the solution;V - volume of the solution; MolalityMolality is defined as the number of moles ( is defined as the number of moles (γγ) of solute dissolved per ) of solute dissolved per

kilogram of solventkilogram of solvent.. Thus, the molality of solute in a solution is Thus, the molality of solute in a solution is

Cm = Cm = γ γ = = m msolutesolute ; ; mmsolventsolvent M M solute solute mmsolventsolvent

when Cm – molality (by mole of solute per kilogram of solvent);when Cm – molality (by mole of solute per kilogram of solvent);γ - number of moles of solute;γ - number of moles of solute;m – mass of solvent.m – mass of solvent.

In measure analysis for the characteristic the composition of In measure analysis for the characteristic the composition of solution will use solution will use molar mass of an equivalent (equivalent mass)molar mass of an equivalent (equivalent mass)

Molar mass of an equivalent Molar mass of an equivalent of element is the mass of the of element is the mass of the element which combines with or displaces 1.008 parts by mass of element which combines with or displaces 1.008 parts by mass of hydrogen or 8 part by mass of oxygen or 35.5 parts by mass of hydrogen or 8 part by mass of oxygen or 35.5 parts by mass of chlorine: chlorine: E = fE = fequivalenceequivalence · M · MBB

The factor of equivalence (fThe factor of equivalence (fequivequiv)) - number, which is demonstrated - number, which is demonstrated which part of matter (equivalent) can react with one atom of which part of matter (equivalent) can react with one atom of Hydrogen, or one electron in reduction reactions.Hydrogen, or one electron in reduction reactions.

Molar concentration of an equivalent (normal concentration), Molar concentration of an equivalent (normal concentration), normalitynormality is quantity gram-equivalent of solute per one liter of is quantity gram-equivalent of solute per one liter of solution (V):solution (V):

CCeqeq== γγeqeq = = m . m . V E VV E Vwhere: Cwhere: CMM - - molarity (by mole of solute per liter of a solution); molarity (by mole of solute per liter of a solution);

γγeqeq - number mole-equivalent of solute; - number mole-equivalent of solute;m - mass solute, grams;m - mass solute, grams;E - molar mass of an equivalent solute (equivalent mass of solute);E - molar mass of an equivalent solute (equivalent mass of solute);V - volume of the solution;V - volume of the solution;

Henry's Law:Henry's Law:The solubility of a gas dissolved in a liquid is The solubility of a gas dissolved in a liquid is

proportional to the partial pressure of the gas above proportional to the partial pressure of the gas above the liquid.the liquid.

This is a statement This is a statement of Henry's law,of Henry's law, which can be written which can be written X = KPX = KPX is the equilibrium mole fraction of the gas in solution (its X is the equilibrium mole fraction of the gas in solution (its

solubility)solubility) P is its partial pressure in the gas phaseP is its partial pressure in the gas phase KK - constant of proportionality or - constant of proportionality or Henry's-law constant.Henry's-law constant. The partial pressure is a part of common pressure, The partial pressure is a part of common pressure,

which one is a share of each gas in gas mixture.which one is a share of each gas in gas mixture.

Properties of a solution which depend Properties of a solution which depend only on the concentration of the solute only on the concentration of the solute and not upon its identity are known as and not upon its identity are known as colligative propertiescolligative properties. .

vapor-pressure loweringvapor-pressure lowering boiling-point elevationboiling-point elevation freezing-point depressionfreezing-point depression osmotic pressureosmotic pressure. .

The spontaneous mixing of the particles of the solute The spontaneous mixing of the particles of the solute (present in the solution) and the solvent (present above (present in the solution) and the solvent (present above the solution) to form а homogeneous mixture is called the solution) to form а homogeneous mixture is called diffusiondiffusion, just as the term is used for the spontaneous , just as the term is used for the spontaneous mixing of gases to form homogeneous mixtures. mixing of gases to form homogeneous mixtures.

A A semi-permeable membranesemi-permeable membrane - а membrane which - а membrane which allows the solvent molecules to pass through but not the allows the solvent molecules to pass through but not the solute particles.solute particles.

The net spontaneous flow of the solvent molecules from The net spontaneous flow of the solvent molecules from the solvent to the solution or from a less concentrated the solvent to the solution or from a less concentrated solution to а more concentrated solution through а semi-solution to а more concentrated solution through а semi-permeable membrane is called permeable membrane is called osmosisosmosis (Greek: push). (Greek: push).

The The osmotic pressureosmotic pressure of а solution may thus of а solution may thus be defined as the equivalent of excess be defined as the equivalent of excess pressure which must be applied, to the pressure which must be applied, to the solution in order to prevent the passage of solution in order to prevent the passage of the solvent into it through а semi-permeable the solvent into it through а semi-permeable membrane separating the two, i.e. the membrane separating the two, i.e. the solution and the pure solvent. solution and the pure solvent.

Osmotic pressure may be defined as the Osmotic pressure may be defined as the equilibrium hydrostatic pressure of the equilibrium hydrostatic pressure of the column set up as а result of osmosiscolumn set up as а result of osmosis..

Р Р С; С; Т; Р Т; Р ССТ or P=RТ or P=RCCTT PV= nRT – van’t Hoff equationPV= nRT – van’t Hoff equation for dilute for dilute

solutionssolutions

Laws of osmotic pressureLaws of osmotic pressure - - These are the same as gas These are the same as gas laws and apply to dilute laws and apply to dilute solutions which occur in the solutions which occur in the living bodyliving body

The effect of hypertonic and hypotonic solutions on The effect of hypertonic and hypotonic solutions on animal cells.animal cells.

(а) Hypertonic solutions cause cells to shrink (а) Hypertonic solutions cause cells to shrink (crenation);(crenation);

(b) hypotonic solutions cause cell rupture; (b) hypotonic solutions cause cell rupture;

(c) isotonic solutions cause no changes in cell (c) isotonic solutions cause no changes in cell volume.volume.

The partial vapor pressure of a component in liquid solution is propor tional to The partial vapor pressure of a component in liquid solution is propor tional to the mole fraction of that component, the constant of proportionality being the mole fraction of that component, the constant of proportionality being the vapor pressure of the pure component.the vapor pressure of the pure component.

Raoult's law can be written as Raoult's law can be written as PP11 = X = X1 1 PP11

00

where Pwhere P11 and P and P1100 are the vapor pressure of the solution and that of the pure solvent, are the vapor pressure of the solution and that of the pure solvent,

respectively,respectively,XX11 is the mole fraction of the solvent in the solution. is the mole fraction of the solvent in the solution. PP11 is the total vapor pressure of the solution. is the total vapor pressure of the solution. XX22 = 1 - X = 1 - X22, , PP11 = (1- X = (1- X22)P)P11

00

PP1100 - P - P1 1 isis the the vapor-pressure loweringvapor-pressure lowering

PP1100 - P - P11

---------- = X---------- = X22 fractional vapor-pressure loweringfractional vapor-pressure loweringPP11

00 which can be seen to be equal to the mole fraction of the which can be seen to be equal to the mole fraction of the solute - solute - XX22..

The relationship between boiling-point elevation The relationship between boiling-point elevation and solute concentration: it can be shown that in and solute concentration: it can be shown that in dilute solutions the dilute solutions the boiling-point elevationboiling-point elevation is is proportional to the molality of the solute proportional to the molality of the solute particles. particles.

if if TTbb, represents the boiling-point elevation: , represents the boiling-point elevation:

TTboilingboiling =T=Tboilingboiling (solution) - T(solution) - Tboilingboiling (solvent), (solvent),

TTbb = K = KbbCCmm

CCmm = molality, number of mole of solute per one = molality, number of mole of solute per one kilogram of solventkilogram of solvent

Where:Where: CCmm - molality of the solute in solution - molality of the solute in solution

KKbb- proportionality constant known as the molal - proportionality constant known as the molal boiling-point elevation constant. boiling-point elevation constant.

The relationship between The relationship between freezing-point freezing-point depressiondepression and molality in dilute solutions and molality in dilute solutions is a direct proportionality is a direct proportionality

TTf f = T = Tfreezingfreezing(solvent) (solvent) -- T Tfreezingfreezing(solution) - (solution) - freezing-point depressionfreezing-point depression

TTfreezingfreezing= K= KffCCmm

Where: Where: CCmm - molality of solute; - molality of solute;

KKff - molal freezing-point depression constant - molal freezing-point depression constant

Complex compounds. Complex compounds. Classification of Classification of complex compounds.complex compounds.

ComplexesComplexes are multiple objects, which are formed of more simple objects (ions, molecules), capable to independent existence in solutions.

Coordination compoundsCoordination compounds are the compounds in which the central metal atom is linked to а number of ions or neutral molecules by coordinate bonds i.е. by donation of lone pairs of electrons by these ions or neutral molecules to the central metal atom.

ComplexingComplexing – – it is a process of complex compounds formation from more simple objects.

The term complex in chemistry is usually used to describe molecules or ensembles formed by the combination of ligands and metal ions.

The molecules or ions that surround the central metal ion in a coordination compound are called ligands, and the atoms that are attached directly to the metal are called ligand donor atoms.

The number of ligand donor atoms that surround The number of ligand donor atoms that surround a central metal ion in a complex is called the a central metal ion in a complex is called the coordination numbercoordination number of the metalof the metal

Originally, a complex implied a reversible Originally, a complex implied a reversible association of molecules, atoms, or ions through association of molecules, atoms, or ions through weak chemical bonds.weak chemical bonds.

Some important characteristics of chelates.Some important characteristics of chelates. (i) Chelating ligands form more stable complexes than (i) Chelating ligands form more stable complexes than

the monodentate analogs. This is called the monodentate analogs. This is called chelating chelating effecteffect..

(ii) Chelating ligands, which do not contain double (ii) Chelating ligands, which do not contain double bonds e.g. ethylenediamine form five membered stable bonds e.g. ethylenediamine form five membered stable rings. The chelating ligands such as acetylacetone form rings. The chelating ligands such as acetylacetone form six membered stable ring complexes.six membered stable ring complexes.

(iii) Ligands with large groups form unstable rings than (iii) Ligands with large groups form unstable rings than the ligands with smaller groups due to steric hindrance.the ligands with smaller groups due to steric hindrance.

Coordination number.Coordination number. The total number The total number of monodentate ligands (plus double the of monodentate ligands (plus double the number of bi dentate ligands if any) number of bi dentate ligands if any) attached to the central metal ion through attached to the central metal ion through coordinate bonds is called the coordinate bonds is called the coordination number of the metal ioncoordination number of the metal ion..

[Ag(СN)[Ag(СN)22]]--, [Cu(NН, [Cu(NН33))44]]

2+2+ and [Cr(Н and [Cr(Н22О)О)66]]33

Coordination sphere.Coordination sphere.

The central atom and the ligands which The central atom and the ligands which are directly attached to it are enclosed in are directly attached to it are enclosed in square brackets and are collectively square brackets and are collectively termed as the termed as the coordination sphere.coordination sphere.

Oxidation number or oxidation stateOxidation number or oxidation state.. It is а number that represents an electric charge which an

atom or ion actually has or appears to have when combined with other atoms,

oxidation number of copper in [Cu(NH3)4]2+ is +2 but

coordination number is 4. oxidation number of Fe in [Fe(СN)6]

3- is + 3 but the coordination number is 6.

(i) [Cu (NНЗ)4]SO4. (ii) Fe in [Fe (СN)6]

3-

(iii)К3[Fe(С2О4)3]. (iv) [Ni(CO)4].

Charge on the complex ion.Charge on the complex ion.

The charge carried by а complex ion is the The charge carried by а complex ion is the algebraic sum of the charges carried by algebraic sum of the charges carried by central metal ion and the ligands central metal ion and the ligands coordinated to the central metal ion. coordinated to the central metal ion.

[Ag (CN)[Ag (CN)22]-]-

[Cu (NH[Cu (NH33))44]]2+2+

Charge coordination number example

of the metal ion +1 2

Ag+, Cu+

+2 4, 6 Cu2+, Zn2+, Pd2+, Pt2+

+3 6, 4 Pt4+, Cr3+, Co3+, Fe3+

+4 8 Sn4+

Co-ordination Werner’s theory

Aqueous solutions that contain [Ni(H2O)6]2+, [Ni(NH3)6]2+ and [Ni(en)3]2+ (from left to right). The two solutions on the right were prepared by adding ammonia and ethylenediamine, respectively, to aqueous nickel(II)

nitrate.

Naming Coordination CompoundsNaming Coordination Compounds

Names of Some Common Metallate Names of Some Common Metallate AnionsAnions

Names of Some Common LigandsNames of Some Common Ligands

Examples of Complexes withExamples of Complexes withVarious Coordination NumbersVarious Coordination Numbers

Ligands have at least one lone pair of electrons that can be used to form a coordinate covalent bond to a metal ion.

They can be classified as monodentate monodentate or or polydentatepolydentate,, depending on the number of ligand donor atoms that bond to the metal.

Ligands such as H2O, NH3 or Cl- that bond using the electron pair of a single donor atom are called monodentatemonodentate ligands (literally, “onetoothed” ligands).

Those that bond through electron pairs on more than one donor atom are termed polydentatepolydentate ligands (“many-toothed” ligands).

For example, ethylenediamine (NH2CH2CH2NH2 abbreviated en) is a bidentatebidentate ligand because it bonds to a metal using an electron pair on each of its two nitrogen atoms.

The hexadentatehexadentate ligand ethylenediaminetetraacetate ion (EDTA4-) bonds to a metal ion through electron pairs on six donor atoms (two N atoms and four O atoms).

Structures of some common ligands

Types of complexTypes of complex::

1. 1. Ionic associates (ionic pairs)Ionic associates (ionic pairs) in solutions are in solutions are formed as a result only electrostatic interaction formed as a result only electrostatic interaction between opposite charged ions, for examplebetween opposite charged ions, for example

KtKt++ ++ AnAn--[Kt[Kt++, An, An--]] (CH3)2N N(CH3)2

C

(CH3)2N

C

N(CH3)2

[SbCl6]-+

+

[SbCl6]-

+

Malachite green

2. 2. Complexes without the coordination centreComplexes without the coordination centre

Hydroquinone Hydroquinone Quinhydrone Quinhydrone

QuinoneQuinone

3. 3. Coordination complex compoundsCoordination complex compounds

Coordination complex Coordination complex compounds:compounds:

1.1. One-nuclear complexesOne-nuclear complexes One-ligandly: One-ligandly: metallamine metallamine [Cu(NH[Cu(NH33))44]SO]SO44

aquacomlexes aquacomlexes [Co(H[Co(H22O)O)66]Cl]Cl22

acidocomplexes acidocomplexes KK22[PtCl[PtCl44]; ];

HH22[SiF[SiF66];];

Combination-ligandly: Combination-ligandly: [Pt(NH[Pt(NH33)Cl)Cl22];];

[Pt(NH[Pt(NH33)Cl)Cl33].].

2. Poly-nuclear complexes2. Poly-nuclear complexes bridging complex bridging complex [Cr(NH[Cr(NH33))55-OH-(NH-OH-(NH33))55Cr]ClCr]Cl55

cluster complex cluster complex

isopoly acids isopoly acids НН44РР22ОО77, Н, Н22ВВ44ОО77

heteropoly acids heteropoly acids HH33POPO44·12MoО·12MoО33·nН·nН22OO

HH33POPO44·12WО·12WО33·nН·nН22O O

HH44SiОSiО44·12MoО·12MoО33·nН·nН22OO

HH44SiОSiО44·12WО·12WО33·nН·nН22OO

Re Re

Br Br

Br

Br

Br BrBr

Br

2-

A complex such as [Co(en)3]3+ or Co(EDTA)]- that contains one or more chelate rings is known as a metal chelatechelate.

The resulting five-membered ring consisting of the Co(III) ion, two N atoms, and two C atoms of the ligand is called a chelate ring.chelate ring.

[Co(en)3]3+ Co(EDTA)]-

Scheme of copper Scheme of copper chelationchelation [[CuCu((NHNH33))44]]2+2+

Octahedral structure of theOctahedral structure of the[Co(NH[Co(NH33))66]]3+3+

Idiosyncrasy of chelate – it is presence Idiosyncrasy of chelate – it is presence of cycles.of cycles.

Diethylenediaminocopper (ІІ) Diglycinatocopper (ІІ)

active site of chlorophyll

active site of hemoglobin

hemoglobin

Structure of molecule of cyancobalamin (vitamin В12)

Mechanism of action Tetacinum-calcium

Ions Hg2+ and Cd2+ displace ions Ca2+ from Tetacinum

Color changes produced by adding various reagents to an equilibrium mixture of Fe3+ (pale yellow), SCN- (colorless), and FeNCS2+ (red): (a) The original solution. (b) After adding to FeCl3 the original solution, the red color is darker because of an increase in [FeNCS2+]. (c) After adding KSCN to the original solution, the red color again deepens. (d) After adding H2C2O4 to the original solution, the red color disappears because of a decrease in [FeNCS2+] the yellow color is due to Fe(C2O4)3

3-. (e) After adding HgCl2 to the original solution, the red color again vanishes.

Necessary parts of ligands for chelate Necessary parts of ligands for chelate formationformation

1. 1. Functional-analytical groupsFunctional-analytical groups (FAG) (FAG) - - areare specific groups which provide occurrence of specific groups which provide occurrence of donor-acceptor bond.donor-acceptor bond.

-ОН, -SH, =NH, -COOH, -SO-ОН, -SH, =NH, -COOH, -SO33H, -AsОH, -AsО33HH22, ,

C=Ö: і т.д.C=Ö: і т.д.

2. 2. Analytical-active groupsAnalytical-active groups (ААG) (ААG) – are the groups – are the groups of atoms which change of atoms which change analyticalanalytical properties of properties of reaction products (solubility, intensity of reaction products (solubility, intensity of colouring). colouring).

AuxochromeAuxochrome - this is a group of atoms attached to a - this is a group of atoms attached to a chromophore which modifies the ability of that chromophore which modifies the ability of that chromophore to absorb light. chromophore to absorb light.

An auxochrome is a functional group of atoms with An auxochrome is a functional group of atoms with nonbonded electrons which, when attached to a nonbonded electrons which, when attached to a chromophore, alters both the wavelength and chromophore, alters both the wavelength and intensity of absorption. intensity of absorption.

If these groups are in direct conjugation with the If these groups are in direct conjugation with the pi-systempi-system of the chromophore, they may increase of the chromophore, they may increase the wavelength at which the light is absorbed and the wavelength at which the light is absorbed and as a result intensify the absorption as a result intensify the absorption (-Cl, -Br, -J, -(-Cl, -Br, -J, -CC66HH55)). .

A feature of these auxochromes is the presence of A feature of these auxochromes is the presence of at least one lone pair of electrons which can be at least one lone pair of electrons which can be viewed as extending the conjugated system by viewed as extending the conjugated system by resonance. Also that groups which improve resonance. Also that groups which improve solubility of complexes solubility of complexes (-SO(-SO33H,-COOH).H,-COOH).

Process of complexingProcess of complexing stepwise fashionstepwise fashion cumulative cumulative

(common)(common)

Me + L ↔ MeL Me + L ↔ MeL Me + L ↔ MeL Me + L ↔ MeL

MeL + L ↔ MeLMeL + L ↔ MeL22 Me + 2L ↔ MeL Me + 2L ↔ MeL22

MeLMeL22 + L ↔ MeL + L ↔ MeL33 Me + 3L ↔ MeL Me + 3L ↔ MeL33

·································· ·································· ·································· ··································

MeLMeLn-1n-1+ L ↔ MeL+ L ↔ MeLnn Me + n L ↔MeL Me + n L ↔MeLnnThe formation of a metal–ligand complex is described by a formation constant, Kf.

Process of complex Process of complex dissociatedissociatestepwise fashionstepwise fashion cumulative (common)cumulative (common)

MeLMeLnn MeL MeLn-1n-1+ L + L MeL MeLnn Me + nL Me + nL

MeLMeLn-1n-1 MeL MeLn-2n-2+ L МeL+ L МeLn-1 n-1 Me + (n-1)L Me + (n-1)L

………………………………………….. ……………………..……………………..

MeMeLL22 MeL + L MeL + L Me MeLL22 Me + 2L Me + 2L

MeMeLL Me + L Me + L MeMeLL Me Me +L+L The reverse of reaction complexing is called a

dissociation reaction and is characterized by a dissociation constant, Kd

Stepwise formation constantsThe formation constant for a metal–ligand

complex in which only one ligand is added to the metal ion or to a metal–ligand complex (Ki)

Cumulative formation constant The formation constant for a metal–ligand

complex in which two or more ligands are simultaneously added to a metal ion or to a metal–ligand complex (βi).

For example, the reaction between Cd2+ and NH3 involves four successive reactions

So

Relationship between Kf() and Kd

Me + nL ↔MeLMe + nL ↔MeLnn MeL MeLnn↔Me + nL ↔Me + nL

β (Kf) - formation constant (or stability constant)

! So,! So, Kd, which is the reciprocal of Kf.

]MeL[

]L[]Me[K

n

n'd

n

n

n ]L[]Me[]MeL[

'd

n K

1

2. 2. Stability of complexes and influence Stability of complexes and influence of different factors on it.of different factors on it.

Kinetic stability:Kinetic stability: Labile complexesLabile complexes Inert complexesInert complexes

Thermodynamic stability:Thermodynamic stability:

formation constant ((dissociation constant))

FactorsFactors which influence which influence stability of complex stability of complex

connections:connections:

The ion natureThe ion nature of metal and ligand; of metal and ligand;

The chargeThe charge of an metal ion; of an metal ion;

Ionic radiusIonic radius of the metal-complexing agent; of the metal-complexing agent;

The natureThe nature of medium. of medium.

Influence of different factors on Influence of different factors on complexing in solution.complexing in solution.

1. Ionic strength of solution1. Ionic strength of solution

2. рН 2. рН

3. concentration of ligand3. concentration of ligand

4. temperature4. temperature

5. stranger ions, which form slightly soluble 5. stranger ions, which form slightly soluble compound with metal-complexing agent or compound with metal-complexing agent or ligand.ligand.

3. 3. Influence of complexing on precipitate Influence of complexing on precipitate solubility and oxidation-reduction solubility and oxidation-reduction

potential of system.potential of system.

the solubility of precipitate increasesthe solubility of precipitate increases oxidizing and reducing properties of redox-oxidizing and reducing properties of redox-

pair pair can increase or decreasecan increase or decrease (depending (depending on the nature of comlexes, which will form on the nature of comlexes, which will form with oxidizing and reduction redox-pair with oxidizing and reduction redox-pair forms)forms)

4. 4. Usage of complexing in analytical Usage of complexing in analytical chemistry.chemistry.

masking of іоnsmasking of іоns determination of cations and anionsdetermination of cations and anions separationseparation concentrating and determination of ionsconcentrating and determination of ions precipitation of cations and anions from the solutionsprecipitation of cations and anions from the solutions dissolution of precipitatedissolution of precipitate definition identity of drugs on functional groupsdefinition identity of drugs on functional groups change red-ox potentialchange red-ox potential determination of ions by fluorescence analysisdetermination of ions by fluorescence analysis for fixing of equivalence point in titrimetric analysisfor fixing of equivalence point in titrimetric analysis

Silver chloride is insoluble in water (left) but dissolves on addition of an excess of aqueous ammonia (right).

The qualitative analysisThe qualitative analysis

ChelatometryChelatometry

ComplexonComplexon І І:: nitrilotriaceticnitrilotriacetic acidacid ((tetratetradentatedentate))

HOOC-CH2-NCH2-COOH

CH2-COOH

ComplexonComplexon ІІ ІІ: (: (EDEDТА)ТА) ethylenediaminetetraacetic acid

ComplexonComplexon ІІІ ІІІ:: sodium sodium ethylenediaminetetraacetate (Na-(Na-EDEDТА, ТА, trylon trylon BB, , chelatonchelaton) - Na) - Na22HH22YY

HOOC-CH2

CH2-COOH

CH2-COOH

N-CH2-CH2-NHOOC-CH2 .. ..

HOOC-CH2

CH2-COOH

CH2-COONa

N-CH2-CH2-NNaOOC-CH2 .. ..

Complexon ІVComplexon ІV:: cyclohexyl cyclohexyldiaminetetraacetic acid

All All metal-EDTAmetal-EDTA complexes have a complexes have a 1:11:1

stoichiometrystoichiometry.. These complexes are dissolved in water.These complexes are dissolved in water. Metal-EDTA complexes are named – Metal-EDTA complexes are named – metal metal

complexonatecomplexonate. .

CH2-COOH

CH2-COOH

CH2-COOH

CH2-COOH

N

N

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