Which of the following are paramagnetic? (A) [NiCl4]^2-, (B) Ni(CO)4, (C) [Ni(CN)4]^2-, (D) [Ni(H2O)6]^2+, (E) Ni(PPh3)4. Choose…

Question

Which of the following are paramagnetic? (A) [NiCl4]^2-, (B) Ni(CO)4, (C) [Ni(CN)4]^2-, (D) [Ni(H2O)6]^2+, (E) Ni(PPh3)4.

Choose the correct answer from the options given below:

1. A. A and C only
2. B. B and E only
3. C. A and D only (Correct answer)
4. D. A, D and E only

Correct Answer

Option C — A and D only

Detailed Solution & Explanation

The correct answer is A and D only.

Key Points

• [NiCl$_4$]$^{2-}$: Ni$^{2+}$ (3d$^8$), weak-field Cl$^-$ $\Rightarrow$ $sp^3$, tetrahedral, 2 unpaired electrons — paramagnetic.
• [Ni(H$_2$O)$_6$]$^{2+}$: Ni$^{2+}$ (3d$^8$), $sp^3d^2$, octahedral, 2 unpaired electrons — paramagnetic.
• Ni(CO)$_4$, [Ni(CN)$_4$]$^{2-}$ ($dsp^2$) and Ni(PPh$_3$)$_4$ all have zero unpaired electrons — diamagnetic.
• Hence only A and D are paramagnetic.