Complexes. Compounds in which a metal atom or ion is surrounded by a number of oppositely charged...

ComplexesComplexes

Compounds in which a metal atom or ion is surrounded by a Compounds in which a metal atom or ion is surrounded by a

number of oppositely charged ions or by neutral molecules number of oppositely charged ions or by neutral molecules

All possessing lone pairs of electrons which are available for All possessing lone pairs of electrons which are available for

donation to vacant orbitals of the metal atom or iondonation to vacant orbitals of the metal atom or ion

ComplexesComplexes

StructureStructure

11[Hexaammineplatinum(IV)] chloride[Hexaammineplatinum(IV)] chloride

central ion coordination number

ligand

[Pt(NH3)6]Cl4

complex cationcomplex cation

2 2 Potassium hexachloroplatinate(IV)Potassium hexachloroplatinate(IV)

K2[PtCl6]

central ion coordination number

ligand

complex anioncomplex anion

33Iron(O)pentacarbonylIron(O)pentacarbonyl

central atom coordination number

ligand

[Fe(CO)[Fe(CO)55]]

complex moleculecomplex molecule

Central ions atomsCentral ions atoms

Transition metalsTransition metalsAlkaline earth metalsAlkaline earth metalsAlkaline metalsAlkaline metals

Coordination numbersCoordination numbers

Number of ligands in the firstNumber of ligands in the firstcoordination spherecoordination sphere

Complexes with various coordination numbers

CoordinationCoordination numbernumber

CComplexomplex

2 [Ag(NH3)2]+ [CuCl2]

-

3 [HgI3]-

4 [Zn(NH3)4]2+ [Ni(CN)4]2

-

5 [Ni(CN)5]3- Fe(CO)5

6 [Cr(H2O)6]3+ [Fe(CN)6]

3-

7 [ZrF7]3-

8 [Mo(CN)8]4-

L L

L L

M

GeometryGeometry

L M L

linear (2)tetrahedral (4)

L L

L L

M

square planar (4)

LL

L L

M

L

L

octahedral (6)

Cations Cations

H2N-NH3+

Anions Anions

F- Cl- OH- CN- NO3- NO2

-

Neutral molecules Neutral molecules

H2O NH3 CO

Monodentate LigandsMonodentate Ligands

O HH

Cl - -C N

C O -N C S-

O H

WaterWater AmmoniaAmmonia Chloride Chloride ionion

Cyanide Cyanide ionion

Carbon monoxideCarbon monoxide Thiocyanate Thiocyanate ionion

Hydroxide Hydroxide ionion

H2C CH2

H2N NH2

- O

H2C

H2N

C

O

- O

C C

O O

O-

Ethylenediamine Ethylenediamine (en)(en)

Glycinate ion (glyGlycinate ion (gly--)) Oxalate ionOxalate ion

- O

O

O-N CH2 CH2 N

CH2 C O

O CCH2

O

- C CH2

CH2 C O

O-

Ethylenediaminetetraacetate ion (EDTAEthylenediaminetetraacetate ion (EDTA4-4-))

Polydentate LigandsPolydentate Ligands

ChelatesChelates

Bi- or polydentate ligandsBi- or polydentate ligands

Men+Men+Men+ Men+

Nomenclature IUPACNomenclature IUPAC

11 Cation preceeds anionsCation preceeds anions

22 Ligands preceed central ions or atomsLigands preceed central ions or atoms

33 Anion ligands Anion ligands -o-o ending (hydrox ending (hydroxoo chlor chloroo

cyancyanoohellip)hellip)

44 Cations neutral molecules unchanged Cations neutral molecules unchanged

Exception() aqua ammine carbonyl nitrosylException() aqua ammine carbonyl nitrosyl

55 Complex anions Complex anions -ate-ate ending ending

66 Oxidation state Roman numbersOxidation state Roman numbers

Dissociation of complexesDissociation of complexes

Formula Conductance Number of ions

Numberof

chloride ions

[Pt(NH3)6]Cl4 523523 5 4

[Pt(NH3)5Cl]Cl3 404404 4 3

[Pt(NH3)4Cl2]Cl2 228228 3 2

[Pt(NH3)3Cl3]Cl 9797 2 1

[Pt(NH3)2Cl4] 00 0 0

K[Pt(NH3)Cl5] 108108 2 0

K2[PtCl6] 256256 3 0Molar conductance cm2moacutel 0001M

25degC

Stability constant formationStability constant formation

Properties of metal complex differ from metal ionProperties of metal complex differ from metal ion

11 Colour changingColour changing22 SolubilitySolubility33 Ligand reactionsLigand reactions44 Number of particles dissociationNumber of particles dissociation

Formation constantFormation constant Kstab (stability constant) Kstab (stability constant)

Pl Ag+ + 2NH3 [Ag(NH3)2]+

[Ag(NH3)2]+

[Ag+][NH3]2

= 17107 K =

Dissociation constantDissociation constant

[Kstab]

1Kd =

Constitutional isomers

EnantiomersIonization isomers Diastereoisomers

Stereoisomers

Linkage isomers

Isomers

IzomerismIzomerism

CrCl36H2O

[Cr(H2O)6]Cl3 [Cr(H2O)4Cl2]Cl2H2O

[Cr(H2O)5Cl]Cl2H2O

NH3

NH3

NH3

NH3

Cl

Cl

Co

NH3

NH3

NH3

NH3

Cl

Cl

Co

ciscis transtrans

[dichloro-tetraammine-cobalt(III)] ion

Cl

Cl

Co

en

en

Cl

Cl

Co

en

en

[dichloro-bis(etylenediammine)cobalt(III)] ionen = etylenediammine

Bonding in complexesBonding in complexes

bullValence Bond Theory

bullCrystal Field Theory