Question

Which one of the following complexes is an outer orbital complex

• A. $\left[Co\right(N{H}_3{)}_6{]}^{3+}$
• B. $\left[Mn\right(CN{)}_6{]}^{4-}$
• C. $\left[Fe\right(CN{)}_6{]}^{4-}$
• D. $\left[Ni\right(N{H}_3{)}_6{]}^{2+}$

Answer 1

The correct option is D $\left[Ni\right(N{H}_3{)}_6{]}^{2+}$

Generally, complex having strong filed ligand will act as inner orbital complex. $C{N}^{-}$ is a strong field ligand. $N{H}_3$ act as strong field ligand in $\left[Co\right(N{H}_3{)}_6{]}^{3+}$ and as weak field ligand in $\left[Ni\right(N{H}_3{)}_6{]}^{2+}$.

Complex ion	Hybridization of central atom
$\left[Fe\right(CN{)}_6{]}^{4-}$	$d^{2}s{p}^3$ (inner)
$\left[Mn\right(CN{)}_6{]}^{4-}$	$d^{2}s{p}^3$ (inner)
$\left[Co\right(N{H}_3{)}_6{]}^{3+}$	$d^{2}s{p}^3$ (inner)
$\left[Ni\right(N{H}_3{)}_6{]}^{2+}$	$s{p}^3{d}^2$ (outer)