Chemistry · Coordination Compounds

JEE Main 2026 — 21 January, Morning Shift — Question 59

Given below are two statements : one is labelled as Statement I and the other is labelled as Statement II :

Statement I: Among $\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)^{2+},\left[\mathrm{Ni}(\mathrm{en})_{3}\right)\right]^{2+}$ , $\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}$ and $\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+},\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ , has the maximum number of unpaired electrons.

Statement II: The number of pairs among $\left\{\left[\mathrm{NiCl}_{4}\right]^{2-},\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\right\},\left\{\left[\mathrm{NiCl}_{4}\right]^{2-},\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\right.$ and $\left\{\left[\mathrm{Ni}(\mathrm{CO})_{4}\right], \quad\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\right\} \quad$ that contain only diamagnetic species is two.

In the light of the above statements, choose the correct answer from the options given below:

Option A:
Statement I is false but Statement II is true
Option B:
Both Statement I and Statement II are true
Option C:
Both Statement I and Statement II are false
Option D:
Statement I is true but Statement II is false
Correct

Answer: D

Step-by-step solution

$\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} \Rightarrow \mathrm{d}^{9}, \mathrm{dsp}^{2}$ one unpaired electron $\left[\mathrm{Ni}(\mathrm{en})_{3}\right]^{2+} \Rightarrow \mathrm{d}^{8}, \mathrm{sp}^{3} \mathrm{~d}^{2}$ two unpaired electrons $\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+} \Rightarrow \mathrm{d}^{8}, \mathrm{sp}^{3} \mathrm{~d}^{2}$ two unpaired electrons $\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+} \Rightarrow \mathrm{d}^{5}, \mathrm{sp}^{3} \mathrm{~d}^{2}$ five unpaired electrons $\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]$ (diamagnetic) $\left[\mathrm{NiCl}_{4}\right]^{-2}$ (paramagnetic) $\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{-2}$ (diamagnetic)

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 21 January, Morning Shift
Subject: Chemistry
Chapter: Coordination Compounds
Topic: Properties and importance of Coordination Complexes