Question

Illustrate coordination isomerism in coordination compounds giving one example.

Answer 1

1. Coordination isomerism is a type of isomerism observed in coordination compounds that contain both a cationic and an anionic complex ion. 
2. It arises due to the exchange of ligands between the two metal centres, resulting in isomers with the same overall chemical formula but different distributions of ligands. 
3. For example, consider the pair of coordination compounds:
   [Co(NH₃)₆][Cr(CN)₆] and [Cr(NH₃)₆][Co(CN)₆]
   In the first isomer, the cobalt(III) ion is coordinated with six ammonia (NH₃) ligands, while the chromium(III) ion is coordinated with six cyanide (CN⁻) ligands. In the second isomer, the ligands are exchanged between the metal centres chromium(III) is bonded to NH₃, and cobalt(III) is bonded to CN⁻.
4. Although both isomers have the same molecular formula, they differ in the way ligands are arranged around the metal ions, leading to different chemical properties. This type of isomerism is only possible when both cationic and anionic coordination entities are present in the compound.