Identify the coordination complexes in which the central metal ion has $\mathrm{d}^{4}$ configuration. (A) $\left[\mathrm{FeO}_{4}\right]^{2-}$ (B) $\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-}$ (C) $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$ (D) (see structure) (E) $\left[\mathrm{NiF}_{6}\right]^{2-}$ Choose the correct answer from the options given below :

JEE Main · 2025 · 23 Jan 2025 · Shift 2 · Coordination Compounds

Identify the coordination complexes in which the central metal ion has

d^{4}

configuration.
(A)

[FeO_{4}]^{2 -}

(B)

[Mn (CN)_{6}]^{3 -}

(C)

[Fe (CN)_{6}]^{3 -}

(D) (see structure)
(E)

[NiF_{6}]^{2 -}

Choose the correct answer from the options given below :

Answer: (C)

Assign the oxidation state of the central metal in each species and count its d-electrons. In

[FeO X_{4}]^{2 -}

, iron is +6, so

Fe X^{6 +}

3 d^{2}

. In

[Mn (CN) X_{6}]^{3 -}

, manganese is +3, and

Mn X^{3 +}

3 d^{4}

. In

[Fe (CN) X_{6}]^{3 -}

, iron is +3, and

Fe X^{3 +}

3 d^{5}

. The compound

Cr X_{2} (OOCCH X_{3}) X_{4} (H X_{2} O) X_{2}

is chromous acetate, with chromium in the +2 state;

Cr X^{2 +}

3 d^{4}

. In

[NiF X_{6}]^{2 -}

, nickel is +4, and

Ni X^{4 +}

3 d^{6}

. Only manganese in

[Mn (CN) X_{6}]^{3 -}

and chromium in the acetate complex carry a

d^{4}

configuration.

JEE Main · 2025 · 23 Jan 2025 · Shift 2 · Single correct option