From the magnetic behaviour of [ NiCl 4 ] 2- (paramagnetic) and [ Ni ( CO ) 4 ] (diamagnetic), choose the correct geometry and oxidation state.

[ NiCl 4 ] 2- : Ni II , tetrahedral [ Ni ( CO ) 4 ]: Ni (0) , tetrahedral

[ NiCl 4 ] 2- : Ni II , square planar [ Ni ( CO ) 4 ] : Ni (0) , square planar

[ NiCl 4 ] 2- : Ni II , tetrahedral [ Ni ( CO ) 4 ]: Ni II , square planar

[ NiCl 4 ] 2- : Ni (0) , tetrahedral [ Ni ( CO ) 4 ]: Ni (0) , square planar

Chemistry · Coordination Compounds

JEE Main 2025 — 22 January, Morning Shift — Question 42

From the magnetic behaviour of $\left[\mathrm{NiCl}_{4}\right]^{2-}$ (paramagnetic) and $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]$ (diamagnetic), choose the correct geometry and oxidation state.

Option A:
$\left[\mathrm{NiCl}_{4}\right]^{2-}$ : $\mathrm{Ni}^{\text {II }}$ , square planar $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]$ : $\mathrm{Ni}(0)$ , square planar
Option B:
$\left[\mathrm{NiCl}_{4}\right]^{2-}: \mathrm{Ni}^{\text {II }}$ , tetrahedral $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]: \mathrm{Ni}(0)$ , tetrahedral
Correct
Option C:
$\left[\mathrm{NiCl}_{4}\right]^{2-}$ : $\mathrm{Ni}^{\mathrm{II}}$ , tetrahedral $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]: \mathrm{Ni}^{\mathrm{II}}$ , square planar
Option D:
$\left[\mathrm{NiCl}_{4}\right]^{2-}: \mathrm{Ni}(0)$ , tetrahedral $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]: \mathrm{Ni}(0)$ , square planar

Answer: B

Step-by-step solution

$\left[\mathrm{NiCl}_{4}\right]^{2-}$

$\mathrm{Ni}^{+2}-[\mathrm{Ar}] 3 \mathrm{~d}^{8} 4 \mathrm{~s}^{0} \rightarrow \mathrm{sp}^{3}$ , Tetrahedral

Number of unpaired electron $=2$ paramagentic $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]$ ,

$\mathrm{Ni}(0) \rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^{0}$ (After rearrangement)

No unpaired electron

$\mathrm{sp}^{3}$ , Tetrahedral, Diamagnetic

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 22 January, Morning Shift
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Properties and importance of Coordination Complexes

In which of the following complexes the CFSE, Delta 0 will be equal to zero?

Answer: B

Step-by-step solution

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