6 Shape of complex ions

Shapes of complex ions transition metal ions commonly form octahedral complexes with small ligands (e.g. H2O and NH3 ). transition metal ions commonly form tetrahedral complexes with larger ligands (e.g.Cl- ). square planar complexes are also formed, e.g. cisplatin Ag+ commonly forms linear complexes e.g. [Ag(NH3 )2 ]+ used as Tollen’s Reagent [Co(NH3 )6 ]2 [Cu(H2O)6 ]2+ [CoCl4 ]2- Isomerism in complex ions Complexes can show two types of stereoisomerism: cis-trans isomerism and optical isomerism Ni NH3 Cl H3N Cl Ni Cl NH3 H3N Cl Cis-[Cr(H2O )4Cl2 ]+ trans-Ni(NH3)2Cl2 Cis-trans isomerism in square planar complexes H3N Ag NH3 Pt + Cl Cl H3N Ni H3N NH3 NH3 H3N H3N NH3 NH3 2+ 2- Cu Cl Cl Cl Cl Complexes with 3 bidentate ligands can form two optical isomers (non-superimposable mirror images). 2+ CH2 CH2 NH2 NH2 CH2 CH2 H2N H2C NH2 H2C NH2 NH2 NiOptical isomerism in octahedral complexes Cis-trans isomerism in octahedral complexes cis–trans isomerism is a special case of E–Z isomerism HCl Cr2+ OH2 OH2 H2O OH2 ClH HCl Cr2+ OH2 OH2 H2O OH2 ClH Cis-Ni(NH3)2Cl2 trans-[Cr(H2O)4Cl2 ]+ + + 2 Ag+ commonly forms linear complexes e.g. [Ag(H2O)2 ]+ [Ag(NH3 )2 ]+ , [Ag(S2O3 )2 ]3- and [Ag(CN)2 ] – All are colourless solutions