Coordination Compounds - Result Question 51

####57. Of the following complex ions, which is diamagnetic in nature?

[2011]

(a) [NiCl4]2

(b) [Ni(CN)4]2

(c) [CuCl4]2

(d) [CoF6]3

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Solution:

  1. (b) Ni2+=3d84s

Since, the coordination number of Ni in this complex is 4 , the configuration of Ni2+ at first sight shows that the complex is paramagnetic with two unpaired electron. However, experiments show that the complex is diamagnetic. This is possible when the 3d electrons rearrange against the Hund’s rule as shown below. This is in

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accordance with the fact that the ligand involved here is strong i.e., CNion.

Ni2+ (after rearrangement)

Hence, now dsp2 hybridization involving one 3d, one 4s and two 4p orbitals, takes place leading to four dsp2 hybrid orbitals, each of which accepts four electron pairs from CNion forming [Ni(CN)4]2 ion.

[Ni(CN)4]2

Thus, the complex is diamagnetic as it has no unpaired electron.

58 .

(c) Cr2+,d4

4 unpaired es

Mn2+,d5

5 unpaired es

4 unpaired es

3 unpaired es

Minimum paramagnetic behaviour =[Co(H2O)6]2+



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