Chemistry · Coordination Compounds

JEE Main 2026 — 4 April, Evening Shift — Question 57

Consider the metal complexes $\left[\mathrm{Ni}(\mathrm{en})_{3}\right]^{2+}(\mathrm{A})$ , $\left[\mathrm{NiCl}_{4}\right]^{2-}(\mathrm{B})$ and $\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}(\mathrm{C})$ . Choose the CORRECT option by considering the number of unpaired electron present in (A), (B) and (C) respectively and the order of frequency of absorption.

Option A:
2, 2, 2 and $(\mathrm{A})>(\mathrm{C})>(\mathrm{B})$
Correct
Option B:
0,2,0 and $(\mathrm{A})>(\mathrm{C})>$ (B)
Option C:
2, 2, 0 and (B) $>$ (C) $>$ (A)
Option D:
2, 2, 2 and $(\mathrm{C})>$ (A) $>$ (B)

Answer: A

Step-by-step solution

A) $\mathrm{Ni}^{2+} \Rightarrow 3 \mathrm{~d}^{8}, \mathrm{SFL}, \mathrm{t}_{2 \mathrm{~g}}^{2,2,2} \mathrm{e}_{\mathrm{g}}^{1,1} \Rightarrow$ unpaired $\mathrm{e}^{-}=2$ (B) $\mathrm{Ni}^{2+} \Rightarrow 3 \mathrm{~d}^{8}$ , WFL , tetrahedral, $\mathrm{e}^{2,2} \mathrm{t}_{2}^{2,1,1}$

⇒ unpaired $\mathrm{e}^{-}=2$ (C) $\mathrm{Ni}^{2+} \Rightarrow 3 \mathrm{~d}^{8}$ , SFL , $\mathrm{t}_{2 \mathrm{~g}}^{2,2,2} \mathrm{e}_{\mathrm{g}}^{1,1} \Rightarrow$ unpaired $\mathrm{e}^{-}=2$

As $\Delta_{\mathrm{o}}>\Delta_{\mathrm{t}}$ and Ligand strength : en $>\mathrm{NH}_{3}>\mathrm{Cl}^{-}$ Strength of ligand increases, $\Delta$ increases, hence more is the frequency required of absorption.

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 4 April, Evening Shift
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Theories of Bonding in Coordination Compounds