Question

Among $\left[Ni\right(CO{)}_4],[Ci(CN{)}_4{]}^{2-}$ and $\left[Ni\right(Cl{)}_4{]}^{2-}$.

• A. $\left[Ni\right(CO{)}_4]$ and $[NiC{l}_4{]}^{2-}$ and diamagnetic and $\left[Ni\right(CN{)}_4{]}^{2-}$ is paramagnetic
• B. $[NiC{l}_4{]}^{2-}$ and $\left[Ni\right(CN{)}_4{]}^{2-}$ are diamagnetic and $\left[Ni\right(CO{)}_4]$ is paramagnetic
• C. $\left[Ni\right(CO{)}_4]$ and $\left[Ni\right(CN{)}_4{]}^{2-}$ are diamagnetic and $[NiC{l}_4{]}^{2-}$ is paramagnetic
• D. $\left[Ni\right(CO{)}_4]$ is diamagnetic and $[NiC{l}_4{]}^{2-}$ and $\left[Ni\right(CN{)}_4{]}^{2-}$ are paramagnetic

Answer 1

The correct option is C $\left[Ni\right(CO{)}_4]$ and $\left[Ni\right(CN{)}_4{]}^{2-}$ are diamagnetic and $[NiC{l}_4{]}^{2-}$ is paramagnetic

In the given complexes majorly 3 ligands are there and among them, CO and $C{N}^{-}$ are the strong field ligands and $C{l}^{-}$ is a weak field ligand. Therefore CO and $C{N}^{-}$ cause pairing of electrons whereas there is no such effect seen in the complex having $C{l}^{-}$ as the ligand hence, $\left[Ni\right(CO{)}_4\left]and\right[Ni(CN{)}_4{]}^{2-}$ are diamagnetic and $\left[Ni\right(Cl{)}_4{]}^{2-}$ is paramagnetic.

Hence option (C) is correct.