Which of the following complexes will show coordination isomerism ? A. [Ag(NH3)2][Ag(CN)2] B. [Co(NH3)6][Cr(CN)6] C. [Co(NH3)6][Co(CN)6] D. [Fe(NH3)6][Co(CN)6] E. [Co(NH3)6][Fe(CN)6] Choose the correct answer from the options given below :

The correct answer is Option 2. Full mathematical solution steps and hints are accessible in the interactive StemCET workspace.

Chemistry Q61 – JEE-MAIN 2026

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Home Chemistry Coordination CompoundsQuestion #320

Which of the following complexes will show coordination isomerism ? A.

[A g (N H_{3})_{2}] [A g (C N)_{2}]

[C o (N H_{3})_{6}] [C r (C N)_{6}]

[C o (N H_{3})_{6}] [C o (C N)_{6}]

[F e (N H_{3})_{6}] [C o (C N)_{6}]

[C o (N H_{3})_{6}] [F e (C N)_{6}]

Choose the correct answer from the options given below :

Clue 1 of 3: Definition of Coordination Isomerism

This type of isomerism occurs in compounds containing both a complex cation and a complex anion, where ligands can be exchanged between the two metal centers.

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Ninja Strategy•Focus on Different Metals

Quickly identify the complexes where the cationic and anionic parts have different central metal atoms; these are the definitive examples of coordination isomerism.

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Step 1: Define Coordination Isomerism✦ Active

Coordination isomerism is a type of structural isomerism that occurs in salts where both the cation and the anion are complex ions. The isomers arise from the interchange of ligands between the two coordination spheres (the cationic and anionic parts).

Step 2: Analyze Each Complex○ Expand

For coordination isomerism to be clearly exhibited, there must be a possibility of forming a distinct new compound by exchanging ligands. This is most unambiguous when the central metal ions in the cation and anion are different.

A. $[A g (N H_{3})_{2}] [A g (C N)_{2}]$ : Both cation and anion have the same metal, Ag. Exchanging ligands would result in the same compound, so it does not show this isomerism in the typical sense.

B. $[C o (N H_{3})_{6}] [C r (C N)_{6}]$ : The metals are different (Co and Cr). Exchanging ligands gives $[C r (N H_{3})_{6}] [C o (C N)_{6}]$ , which is a distinct isomer. So, B shows coordination isomerism.

C. $[C o (N H_{3})_{6}] [C o (C N)_{6}]$ : Both cation and anion have the same metal, Co. Similar to A, this is not a clear case.

D. $[F e (N H_{3})_{6}] [C o (C N)_{6}]$ : The metals are different (Fe and Co). Exchanging ligands gives $[C o (N H_{3})_{6}] [F e (C N)_{6}]$ , a distinct isomer. So, D shows coordination isomerism.

E. $[C o (N H_{3})_{6}] [F e (C N)_{6}]$ : The metals are different (Co and Fe). This is the isomer of D. So, E also shows coordination isomerism.

Step 3: Identify the Correct Combination○ Expand

The complexes that clearly show coordination isomerism are those with different central metal ions in the cationic and anionic parts. These are B, D, and E. Therefore, the correct option includes only these three.

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Chemistry Question 61 – JEE-MAIN 2026

Clue 1 of 3: Definition of Coordination Isomerism

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