Question

Which of the following is expected to be a paramagnetic complex ?

• A. $[Ni(H_{2}O{)}_6{]}^{2+}$
• B. $[Ni(CO{)}_4]$
• C. $[Zn(N{H}_3{)}_4{]}^{2+}$
• D. $[Co(N{H}_3{)}_6{]}^{3+}.$

Answer 1

Answer: (A)

In, $[Ni(H_{2}O{)}_6{]}^{2+}$ configuration of $N{i}^{2+}$ is $[A{r}^{18}]3d^8$. Hybridisation is $s{p}^3{d}^2$ . There are two unpaired electrons and hence complex is paramagnetic.
For structure of $Ni(CO{)}_4$ see Q. 44 above. It is diamagnetic.
In $[Zn(N{H}_3{)}_4{]}^{2+},Z{n}^{2+}$ has configuration of $[A{r}^{18}]3d^{10}$. It is diamagnetic.
For structure of $[Co(N{H}_3{)}_6{]}^{3+}$. See Q. 26. It is diamagnetic.