( iii) Ionisation isomerism This isomerism arise due to exchange of ionisable anion with anionic ligand. e. g..
( iv) Solvate isomerism This is also known as hydrate isomerism. In this isomerism, water is taken as solvent. It has different number of water molecules in the coordination sphere and outside it. e. g..
[ Co( H2O) 6 ] CI3, [ Co( H2O) 4C12 ] Cl ยท 2H2O, [ Co( H2O) 3Cl3 ]. 3H2O
2. Stereoisomerism
Stereoisomers have the same chemical formula and chemical bonds but they have different spatial arrangement. These are of two types
( i) Geometrical isomerism Geometrical isomers are of two types i. e., cis and trans isomers. This isomensm is common in complexes with coordination number 4 and 6.
Geometrical isomerism in complexes with coordination number 4( i) Tetrahedral complexes do not show geometrical isomerism.
( ii) Square planar complexes of formula [ MX2L2 ]( X and L are unidentate) show geometrical isomerism. The two X ligands may be arranged adjacent to each other in a cis isomer, or opposite to each other in a trans isomer, e. g.,
( iii) Square planar complex of the type [ MABXL ]( where A, B, X, L, are unidentate ligands) shows three isomers, two cis and one trans.
e. g., [ Pt( NH3)( Br)( Cl)( Py)].