Question

Which of the following has a square planar structure?

• A. $\left[Ni{\left(CO\right)}_4\right]$
• B. ${\left[Ni{\left(Cl\right)}_4\right]}^{2-}$
• C. ${\left[Ni{\left(CN\right)}_4\right]}^{2-}$
• D. All of the above

Answer 1

Answer: (C)

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

$\left[Ni{\left(CO\right)}_4\right]$ - has a tetrahedral structure.
${\left[Ni{\left(Cl\right)}_4\right]}^{2-}$ - has a tetrahedral structure.
${\left[Ni{\left(CN\right)}_4\right]}^{2-}$- has a square planar structure.

In ${\left[Ni{\left(CN\right)}_4\right]}^{2-}$, Ni is in +2 state
$N{i}^{2+}\Rightarrow \left[Ar\right]4s^{0}3d^8\Rightarrow 4s^{0}3d_{xy}^{2}3d_{yz}^{2}3d_{zx}^{2}3d_{z^2}^{2}3d_{x^2-y^2}^0$ $[\because \text{The ligand is strong it will pair up single electrons in the d-orbital}]$
Hence the hybridization would be $ds{p}^2$ and the structure is $\text{square planar structure}$.
Option C.