Of the following complex ions, which is diamagnetic in nature?
- [NiCl4]2-
- [Ni(CN)4]2-
- [CuCl4]2-
- [CoF6]3-
Answer
(2) [Ni(CN)4]2-
Solution
(1) [NiCl4]2-: Ni2+ (3d8), Cl- weak field sp3, tetrahedral, 2 unpaired electrons paramagnetic.
(2) [Ni(CN)4]2-: CN- strong field pairs the 3d electrons dsp2, square planar, no unpaired electron diamagnetic.
(3) [CuCl4]2-: Cu2+ (3d9) always has 1 unpaired electron paramagnetic.
(4) [CoF6]3-: Co3+ (3d6), F- weak field sp3d2, 4 unpaired electrons paramagnetic.
Answer: (2)