Complexes

Complexes Compounds in which a metal atom or ion is surrounded by a number of oppositely charged ions or by neutral molecules. All possessing lone pairs of electrons which are available for donation to vacant orbitals of the metal atom or ion.

[Hexaammineplatinum(IV)] chloride Structure 1. [Hexaammineplatinum(IV)] chloride central ion coordination number ligand [Pt(NH3)6]Cl4 complex cation

Potassium hexachloroplatinate(IV) 2. Potassium hexachloroplatinate(IV) K2[PtCl6] central ion coordination number ligand complex anion

Iron(O)pentacarbonyl 3. Iron(O)pentacarbonyl central atom coordination number ligand [Fe(CO)5] complex molecule

Central ions, atoms: Transition metals Alkaline earth metals Alkaline metals Coordination numbers: Number of ligands in the first coordination sphere

Complexes with various coordination numbers 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-

Geometry: linear (2) tetrahedral (4) square planar (4) octahedral (6)

Monodentate Ligands Cations: H2N-NH3+ Anions: F-, Cl-, OH-, CN-, NO3-, NO2- Neutral molecules: H2O, NH3, CO

Water Ammonia Chloride ion Cyanide ion Carbon monoxide Thiocyanate ion Hydroxide ion

Polydentate Ligands Ethylenediamine (en) Glycinate ion (gly-) Oxalate ion Ethylenediaminetetraacetate ion (EDTA4-)

Chelates Bi- or polydentate ligands Men+

Nomenclature: IUPAC Cation preceeds anions Ligands preceed central ions or atoms Anion ligands: -o ending (hydroxo, chloro, cyano…) Cations, neutral molecules: unchanged Exception(!): aqua, ammine, carbonyl, nitrosyl Complex anions: -ate ending Oxidation state: Roman numbers

Dissociation of complexes Formula Conductance* Number of ions Number of chloride ions [Pt(NH3)6]Cl4 523 5 4 [Pt(NH3)5Cl]Cl3 404 3 [Pt(NH3)4Cl2]Cl2 228 2 [Pt(NH3)3Cl3]Cl 97 1 [Pt(NH3)2Cl4] K[Pt(NH3)Cl5] 108 K2[PtCl6] 256 *Molar conductance: cm2/·mól, 0,001M, 25°C

Stability constant, formation Properties of metal complex differ from metal ion! Colour changing Solubility Ligand reactions Number of particles, dissociation Formation constant: Kstab (stability constant) Pl.: Ag+ + 2NH3 [Ag(NH3)2]+ [Ag(NH3)2]+ [Ag+][NH3]2 = 1,7·107 K = Dissociation constant: [Kstab] 1 Kd =

Constitutional isomers Izomerism Constitutional isomers Enantiomers Ionization isomers Diastereoisomers Stereoisomers Linkage isomers Isomers

CrCl3·6H2O [Cr(H2O)6]Cl3 [Cr(H2O)4Cl2]Cl·2H2O [Cr(H2O)5Cl]Cl2·H2O

[dichloro-tetraammine-cobalt(III)] ion cis trans NH3 Cl Co  NH3 Cl Co  [dichloro-tetraammine-cobalt(III)] ion

[dichloro-bis(etylenediammine)cobalt(III)] ion Cl Co en Cl Co en [dichloro-bis(etylenediammine)cobalt(III)] ion en = etylenediammine

Bonding in complexes: Valence Bond Theory Crystal Field Theory