( 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 )].