In which of the following complexes the CFSE, will be equal to zero? [2025]

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Q.
In which of the following complexes the CFSE, $Δ_{o}$ will be equal to zero [2025]

1 $[Fe {(en)}_{3}] {Cl}_{3}$

2 $[Fe {({NH}_{3})}_{6}] {Br}_{2}$

3 $K_{3} [Fe {(SCN)}_{6}]$

4 $K_{4} [Fe {(CN)}_{6}]$

Ans.
(3)

Complex Ion Ligand type Electronic configuration of ion after octahedral splitting CFSE

$[Fe {(en)}_{3}] {Cl}_{3}$ ${Fe}^{3 +} ({}_{18}{[Ar]} 3 d^{5})$ Strong field $t_{2 g}^{2, 2, 1} e_{g}^{0, 0}$ $5 \times (- 0.4 Δ_{0}) + 2 P$

$[Fe {({NH}_{3})}_{6}] {Br}_{2}$ ${Fe}^{2 +} ({}_{18}{[Ar]} 3 d^{6})$ Strong field $t_{2 g}^{2, 2, 2} e_{g}^{0, 0}$ $6 \times (- 0.4 Δ_{0}) + 2 P$

$K_{3} [Fe {(SCN)}_{6}]$ ${Fe}^{3 +} ({}_{18}{[Ar]} 3 d^{5})$ Weak field $t_{2 g}^{1, 1, 1} e_{g}^{1, 1}$ $3 \times (- 0.4 Δ_{0}) + 2 \times 0.6 Δ_{0} = 0$

$K_{4} [Fe {(CN)}_{6}]$ ${Fe}^{2 +} ({}_{18}{[Ar]} 3 d^{6})$ Strong field $t_{2 g}^{2, 2, 1} e_{g}^{0, 0}$ $6 \times (- 0.4 Δ_{0}) + 2 P$

Solution

Q.
In which of the following complexes the CFSE, $Δ_{o}$ will be equal to zero [2025]

1 $[Fe {(en)}_{3}] {Cl}_{3}$

2 $[Fe {({NH}_{3})}_{6}] {Br}_{2}$

3 $K_{3} [Fe {(SCN)}_{6}]$

4 $K_{4} [Fe {(CN)}_{6}]$

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Complex	Ion	Ligand type	Electronic configuration of ion after octahedral splitting	CFSE
$[Fe {(en)}_{3}] {Cl}_{3}$	${Fe}^{3 +} ({}_{18}{[Ar]} 3 d^{5})$	Strong field	$t_{2 g}^{2, 2, 1} e_{g}^{0, 0}$	$5 \times (- 0.4 Δ_{0}) + 2 P$
$[Fe {({NH}_{3})}_{6}] {Br}_{2}$	${Fe}^{2 +} ({}_{18}{[Ar]} 3 d^{6})$	Strong field	$t_{2 g}^{2, 2, 2} e_{g}^{0, 0}$	$6 \times (- 0.4 Δ_{0}) + 2 P$
$K_{3} [Fe {(SCN)}_{6}]$	${Fe}^{3 +} ({}_{18}{[Ar]} 3 d^{5})$	Weak field	$t_{2 g}^{1, 1, 1} e_{g}^{1, 1}$	$3 \times (- 0.4 Δ_{0}) + 2 \times 0.6 Δ_{0} = 0$
$K_{4} [Fe {(CN)}_{6}]$	${Fe}^{2 +} ({}_{18}{[Ar]} 3 d^{6})$	Strong field	$t_{2 g}^{2, 2, 1} e_{g}^{0, 0}$	$6 \times (- 0.4 Δ_{0}) + 2 P$

Solution

Q. In which of the following complexes the CFSE, Δo will be equal to zero [2025]

1 [Fe(en)3]Cl3

2 [Fe(NH3)6]Br2

3 K3[Fe(SCN)6]

4 K4[Fe(CN)6]

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Q.
In which of the following complexes the CFSE, $Δ_{o}$ will be equal to zero [2025]

1 $[Fe {(en)}_{3}] {Cl}_{3}$

2 $[Fe {({NH}_{3})}_{6}] {Br}_{2}$

3 $K_{3} [Fe {(SCN)}_{6}]$

4 $K_{4} [Fe {(CN)}_{6}]$