Question

The complex compounds [Co(NH₃)₅SO₄]Br and [Co(NH₃)₅Br]SO₄ are:

• A. Coordination isomers
• B. Geometrical isomers
• C. Optical isomers
• D. Ionisation isomer

Answer 1

The Correct Option is D

• Ionisation isomers are compounds that have the same formula but differ in the ions that are present in the solution. This happens when the exchange of ligands between the coordination sphere of the metal and the ionic lattice leads to the formation of different ions in the solution.
• In the given question, the two complex compounds are [Co(NH₃)₅SO₄]Br and [Co(NH₃)₅Br]SO₄. These complexes differ in the way the sulfate (SO₄²⁻) and bromide (Br⁻) ions are coordinated to the cobalt ion in the coordination sphere and the ions in the lattice. As a result, they are ionisation isomers, because they produce different ions when dissolved in solution.

Thus, the correct answer is (D) Ionisation isomer.

Answer 2

Ionisation isomers occur when the same ligands are attached to the central metal ion, but they differ in the counterions (such as SO₄²⁻ and Br⁻ in this case). Here, both complexes have the same composition but differ in the counterions associated with the complex cation, resulting in ionisation isomerism.