Question

Illustrate:

Ionisation isomerism in coordination compounds.

Answer 1

Ionisation isomerism occurs in coordination compounds that have the same molecular formula but produce different ions in solution due to the interaction of a ligand inside the coordination sphere with an ion outside it.

For example, the compounds [Co(NH₃)₅Br]SO₄ and [Co(NH₃)₅SO₄]Br are ionisation isomers. In the first compound, bromide is coordinated to the metal and sulphate is the counter ion, while in the second, sulphate is coordinated and bromide is the counter ion. When dissolved in water, they give different ions: the first gives \[\ce{SO^2-_4}\] ions, and the second gives Br⁻ ions, which can be identified using appropriate chemical tests.