Question

Which of the following complexes is outer orbital complex?

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

Answer 1

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

Generally weaker field ligands form outer orbital complex.

$C{N}^{-}$ is a very strong ligand and $N{H}_3$ is weak ligand.

So $\left[Co\right(N{H}_3{)}_6{]}^{3+}$ and $\left[Ni\right(N{H}_3{)}_6{]}^{2+}$ can form outer orbital complex.

Electronic configuration of $C{o}^{+3}$ is $\left[Ar\right]3d^{6}4s^0$

Electronic configuration of $N{i}^{+2}$ is $\left[Ar\right]3d^{8}4s^0$

Nickel complex can form due to presence of $d^8$ configuration.