Chemistry · Coordination Compounds

JEE Main 2026 — 28 January, Morning Shift — Question 59

The correct statement among the following is :

Option A:
$\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ and $\left[\mathrm{NiCl}_{4}\right]^{2-}$ are diamagnetic and $\mathrm{Ni}(\mathrm{CO})_{4}$ is paramagnetic.
Option B:
$\mathrm{Ni}(\mathrm{CO})_{4}$ and $\left[\mathrm{NiCl}_{4}\right]^{2-}$ are diamagnetic and $\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ is paramagnetic.
Option C:
$\mathrm{Ni}(\mathrm{CO})_{4}$ and $\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ are diamagnetic and $\left[\mathrm{NiCl}_{4}\right]^{2-}$ is paramagnetic.
Correct
Option D:
$\mathrm{Ni}(\mathrm{CO})_{4}$ is diamagnetic and $\left[\mathrm{NiCl}_{4}\right]^{2-}$ and $\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}$ are paramagnetic.

Answer: C

Step-by-step solution

$\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-} \rightarrow 3 \mathrm{~d}^{8} \rightarrow$ diamagnetic $\rightarrow \mathrm{dsp}^{2}$ $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right] \rightarrow 3 \mathrm{~d}^{10} \rightarrow$ diamagnetic $\rightarrow \mathrm{sp}^{3}$ $\left[\mathrm{NiCl}_{4}\right]^{2-} \rightarrow 3 \mathrm{~d}^{8} \rightarrow \mathrm{e}^{2,2} \mathrm{t}_{2}^{2,1,1} \rightarrow \mathrm{sp}^{3} \rightarrow$ paramagnetic.

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Exam: JEE Main 2026
Paper: 28 January, Morning Shift
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Properties and importance of Coordination Complexes

X is the number of geometrical isomers exhibited by [ Pt ( NH 3 ) ( H 2 O ) BrCl ] . Y is the number of optically inactive isomer(s)…

Answer: C

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