Given below are two statements: Statement I: Among $[\mathrm{Cu}(\mathrm{NH}_{3})_{4}]^{2+}$, $[\mathrm{Ni}(\mathrm{en})_{3}]^{2+}$, $[\mathrm{Ni}(\mathrm{NH}_{3})_{6}]^{2+}$ and $[\mathrm{Mn}(\mathrm{H}_{2} \mathrm{O})_{6}]^{2+}$, $[\mathrm{Mn}(\mathrm{H}_{2} \mathrm{O})_{6}]^{2+}$ has the maximum number of unpaired electrons. Statement II: The number of pairs among $\{[\mathrm{NiCl}_{4}]^{2-},[\mathrm{Ni}(\mathrm{CO})_{4}]\}$, $\{[\mathrm{NiCl}_{4}]^{2-},[\mathrm{Ni}(\mathrm{CN})_{4}]^{2-}\}$ and $\{[\mathrm{Ni}(\mathrm{CO})_{4}], [\mathrm{Ni}(\mathrm{CN})_{4}]^{2-}\}$ that contain only diamagnetic species is two. In the light of the above statements, choose the correct answer from the options given below:

(D) Statement I is true but Statement II is false

(A) Statement I is false but Statement II is true

(B) Both Statement I and Statement II are true

(C) Both Statement I and Statement II are false

JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Coordination Compounds

Given below are two statements:

Statement I: Among

[Cu (NH_{3})_{4}]^{2 +}

[Ni (en)_{3}]^{2 +}

[Ni (NH_{3})_{6}]^{2 +}

and

[Mn (H_{2} O)_{6}]^{2 +}

[Mn (H_{2} O)_{6}]^{2 +}

has the maximum number of unpaired electrons.

Statement II: The number of pairs among

{[NiCl_{4}]^{2 -}, [Ni (CO)_{4}]}

{[NiCl_{4}]^{2 -}, [Ni (CN)_{4}]^{2 -}}

and

{[Ni (CO)_{4}], [Ni (CN)_{4}]^{2 -}}

that contain only diamagnetic species is two.

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

Answer: (D)

The unpaired-electron counts are:

[Cu (N H_{3})_{4}]^{2 +}

(

d^{9}

) one,

[Ni (en)_{3}]^{2 +}

and

[Ni (N H_{3})_{6}]^{2 +}

(

d^{8}

) two each, and

[Mn (H_{2} O)_{6}]^{2 +}

(

d^{5}

, weak field) five. The manganese complex has the maximum, so Statement I is correct. For the pairs,

[Ni (CO)_{4}]

(Ni

^{0}

d^{10}

) and

[Ni (CN)_{4}]^{2 -}

(square planar) are diamagnetic, while

[NiC l_{4}]^{2 -}

is tetrahedral and paramagnetic; only the pair

{[Ni (CO)_{4}], [Ni (CN)_{4}]^{2 -}}

contains only diamagnetic species, that is one pair and not two, so Statement II is false. Statement I is true but Statement II is false.

JEE Main · 2026 · 21 Jan 2026 · Shift 1 · Single correct option