Question

Which is most stable complex of $Ni$?

• A. $\left[Ni\right(CN{)}_4{]}^{2-}$
• B. $\left[Ni\right(CN{)}_6{]}^{2-}$
• C. $\left[Ni\right(CN{)}_3{]}^{-}$
• D. $\left[Ni\right(CO{)}_6]$

Answer 1

Answer: (A)

$\left[Ni\right(CN{)}_4{]}^{2-}$

The sum of the first and second ionization energies $I{E}_1+I{E}_2$ is less for Ni. This means that Ni (II) compounds are easily formed.
Also, as $C{N}^{-}$ is strong ligand so Ni will form $ds{p}^2$ square planar complex $\left[Ni\right(CN{)}_4{]}^{2-}$.

Hence, option $\left(A\right)$ is correct.