Coordination Isomerism

Coordination isomerism arises in a compound that is built from both a cationic coordination entity and an anionic coordination entity, each centred on a different metal. This type of isomerism results from the interchange of ligands between the cationic and anionic entities of the two different metal ions present in the compound.

Example

Consider the compound $[Co(NH_3)_6][Cr(CN)_6]$. Here the six $NH_3$ ligands are bound to $Co^{3+}$ (the cationic entity) while the six $CN^{-}$ ligands are bound to $Cr^{3+}$ (the anionic entity).

Its coordination isomer, $[Cr(NH_3)_6][Co(CN)_6]$, has the ligand assignment reversed: the $NH_3$ ligands are now bound to $Cr^{3+}$, and the $CN^{-}$ ligands are bound to $Co^{3+}$. …