This type of isomerism arises from the interchange of ligands between
cationic and anionic entities of different metal ions present in a complex An example is provided by [Co(NH3)6][Cr(CN)6], in which the NH3 ligands
are bound to Co
3+ and the CN
– ligands to Cr
3+ In its coordination
isomer [Cr(NH3)6][Co(CN)6], the NH3 ligands are bound to Cr
3+ and the
CN
– ligands to Co
3+ This form of isomerism arises when the counter ion in a complex salt
is itself a potential ligand and can displace a ligand which can then
become the counter ion