Chemistry - Coordination Chemistry Question with Solution | TestHub

The pair in option (C) consists of $[Co(N{H}_3{)}_4(H_{2}O)Cl]C{l}_2$ and $[Co(N{H}_3{)}_{4}C{l}_2]Cl\cdot H_{2}O$, which are hydrate isomers. For both isomers to have two stereoisomeric forms, they must exhibit geometrical isomerism (cis/trans).

$[Co(N{H}_3{)}_4(H_{2}O)Cl{]}^{2+}$: This is an $M{A}_{4}BC$ type octahedral complex, which exists as cis and trans isomers.

$[Co(N{H}_3{)}_{4}C{l}_2]$⁺: This is an $M{A}_4{B}_2$ type octahedral complex, which also exists as cis and trans isomers.

Since both complexes in this pair can form two distinct geometrical isomers, option (C) is the correct answer.