Q. Define Ionisation Isomerism?

Ionisation Isomerism: when coordinated ions exchange positions with ions present in the lattice position, we get ionisation isomers. Thus compounds having the same chemical composition give different ions in solution For example, a compound [Co(NH₃)₅BrS0₄  which is violet in colour yields [co(NH₃)₅Br²⁺ and SO^2-₄ions in solution, whereas a red  isomer of the compound [co(NH₃)₅Br²produces [CO(NH₃)₅SO₄⁺ and Br ions in  solution. Other examples are:

[Co(en)₂(N0₂)CIlN0₂ and [Co(en) ₂ (N0₂]CI

[Pt(NH₃)₅cI₂IBr₂ and [Pt(NH₃)₄Br₂]Cl₂ etc.