Which of the following coordination complexes exhibits ionization isomerism?

Step-by-step solution

Ionization isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace a ligand which can then become the counter ion. Among the given options, [ Co ( NH ₃)₅( SO ₄)] Br has a counter ion ( Br ^- ) that can exchange with the sulfate ligand ( SO ₄²⁻ ) inside the coordination sphere to form the ionization isomer [ Co ( NH ₃)₅ Br ] SO ₄ . [ Pt ( NH ₃)₂ Cl ₂] exhibits geometrical isomerism (cis and trans forms). [ Co ( en )₃] Cl ₃ exhibits optical isomerism due to the lack of a