What type of isomerism exists in compounds containing two or more complexes, each of which contains a different set of ligands that can in principle be replaced with a ligand of the other complex?

Correct option is A

• Coordination isomerism occurs when two complexes with the same formula but different ligands are present in the same compound. In this type of isomerism, the ligands can be interchanged between the metal centers, leading to different isomers.

• The key characteristic of coordination isomerism is that each complex contains a different set of ligands, and these ligands can, in principle, be exchanged with ligands from the other complex within the compound.

• Example: The compound [Co(NH₃)₆][Cr(CO)₆] can undergo coordination isomerism. The [Co(NH₃)₆] complex can exchange ligands with the [Cr(CO)₆] complex, leading to two different isomers: one where the cobalt complex has the ammonia ligands and the chromium complex has carbonyl ligands, and another where the ligands are exchanged.

• Option B (Solvate Isomerism): Solvate isomerism occurs when the solvent molecules are part of the crystal structure and can be replaced by another solvent. This is not related to the exchange of ligands between different complexes.

• Option C (Linkage Isomerism): Linkage isomerism involves ligands that can bind to the metal center at two different sites. This does not involve the exchange of ligands between two different complexes.

• Option D (Ionisation Isomerism): Ionisation isomerism occurs when the ions of a complex can be rearranged in such a way that the overall formula remains the same but the ions that dissociate in solution are different. This is not related to the exchange of ligands between two complexes.