The d-orbital electronic configuration of the complex among $\left[\mathrm{Co}(\mathrm{en})_{3}\right]^{3+},\left[\mathrm{CoF}_{6}\right]^{3-},\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ and $\left[\mathrm{Zn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ that has the highest CFSE is :

JEE Main · 2025 · 02 Apr 2025 · Shift 2 · Coordination Compounds

The d-orbital electronic configuration of the complex among

[Co (en)_{3}]^{3 +}, [CoF_{6}]^{3 -}, [Mn (H_{2} O)_{6}]^{2 +}

and

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

that has the highest CFSE is :

Answer: (A)

Crystal field stabilisation energy is greatest for a strong-field, low-spin

d^{6}

ion.

Co X^{3 +}

3 d^{6}

; with ethylenediamine, a strong-field chelating ligand, the electrons pair in the lower set to give

t_{2 g}^{6} e_{g}^{0}

, the maximum stabilisation.

[CoF X_{6}] X^{3 -}

(

d^{6}

, weak field) is high spin

t_{2 g}^{4} e_{g}^{2}

;

[Mn (H X_{2} O) X_{6}] X^{2 +}

(

d^{5}

, weak field) is

t_{2 g}^{3} e_{g}^{2}

with zero CFSE; and

[Zn (H X_{2} O) X_{6}] X^{2 +}

d^{10}

with zero CFSE. The configuration with the highest CFSE is

t_{2 g}^{6} e_{g}^{0}

JEE Main · 2025 · 02 Apr 2025 · Shift 2 · Single correct option