Which from the following statements about $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$…

Which from the following statements about $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$ complex is NOT correct?
  1. Prior to hybridization $\mathrm{Co}^{3+}$ possesses four unpaired electrons.
  2. This complex has all electrons'paired.
  3. It is a high spin complex.
  4. It is a diamagnetic complex.

Solution

In $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$, oxidation state of cobalt is +3 . Valence shell electronic configuration of $\mathrm{Co}^{3+}$ is represented in box diagram as shown:
Thus, prior to hybridisation, $\mathrm{Co}^{3+}$ possesses 4 unpaired electrons. Complex is low spin, so pairing of electrons will take place and electronic configuration after pairing would be
Six orbitals available for hybridisation are two 3 d , one 4 s , three 4 p orbitals
As all electrons are paired, the complex is diamagnetic.

Asked in: MHT CET 2024 (09 May Shift 1)

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