Which of the following are paramagnetic? A. $\left[\mathrm{NiCl}_4\right]^{2-}$ B. $\mathrm{Ni}(\mathrm{CO})_4$ C. $\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}$ D. $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$ E. $\mathrm{Ni}\left(\mathrm{PPh}_3\right)_4$ Choose the correct answer from the options given below :

• A

  $\text { A and C only }$
• B

  $B \text { and } E \text { only }$
• Correct answer
  C

  $\text { A and D only }$
• D

  $\mathrm{A}, \mathrm{D} \text { and } \mathrm{E} \text { only }$

Solution

(A) $\left[\mathrm{NiCl}_4\right]^{2-} \Rightarrow$ Oxidation state $=+2$ Electronic configuration $=3 d^8 4 s^0$ $\mathrm{Cl}=$ W.F.L. No Pairing
(D) $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$ Oxidation state $=+2$, configuration $=3 \mathrm{~d}^8$ $\mathrm{H}_2 \mathrm{O}$ is W.F.L. No pairing
Hence both are paramagnetic.

Hence, the correct answer is option: 'C'.