Which of the following are paramagnetic ?A. [NiCl4]2– B. Ni(CO)4C. [Ni(CN)4]2– D. [Ni(H2O)6]2+E. Ni (PPh3)4Choose the correct answer from the options givenbelow:

Answer

Ligand Field Effects on Ni²⁺ (d⁸) Complexes and Their Magnetism

Cl⁻ and H₂O are weak-field ligands.
As a result, when Ni²⁺ (d⁸) forms complexes with them, it remains in a high-spin state.

Examples:

• [NiCl₄]²⁻ — tetrahedral
• [Ni(H₂O)₆]²⁺ — octahedral

Each of these retains two Unpaired Electron, so they are paramagnetic.

CO and PPh₃ are strong-field ligands.
In Ni(CO)₄ and Ni(PPh₃)₄, nickel is in the zero oxidation state (Ni(0)) with a d¹⁰ configuration.
These are diamagnetic due to full electron pairing.

CN⁻ is also a strong-field ligand.
In the complex [Ni(CN)₄]²⁻, Ni²⁺ (d⁸) adopts a square planar geometry due to pairing of electrons.
This results in a low-spin configuration, making it diamagnetic.

Conclusion:

Only Complexes A and D are paramagnetic with unpaired electrons.
All others are diamagnetic due to full pairing from strong-field ligands.

“Paramagnetic vs Diamagnetic” Fully explained

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