Question

Jahn-Teller effect is not observed in high spin complexes of

• A. ${\mathrm{d}}^4$
• B. ${\mathrm{d}}^9$
• C. ${\mathrm{d}}^{10}$
• D. ${\mathrm{d}}^7$

Answer 1

The correct option is C

${\mathrm{d}}^{10}$

The explanation for the correct option:

Option (C): ${\mathrm{d}}^{10}$

1. The geometrical distortion of molecules and ions that is associated with particular electron configuration is described by the Jahn-Teller effect, also known as John-Teller distortion.
2. The Jahn-Teller distortion is very weak in the case of unevenly occupied ${\mathrm{t}}_{2\mathrm{g}}$ orbitals because the ${\mathrm{t}}_{2\mathrm{g}}$set does not point directly at the ligands and so the energy gain is significantly lower.
3. Jahn-Teller distortion is frequently considerable for asymmetrically occupied $e_{\mathrm{g}}$ orbitals because they are directed towards the ligands and the energy gain is significantly greater.
4. High spin complexes like ${\mathrm{d}}^3,{\mathrm{d}}^5,{\mathrm{d}}^8$and ${\mathrm{d}}^{10}$ do not exhibit the Jahn-Taller effect.
5. 

1. Jahn-Teller effects are stronger in degenerate electronic states occupying the $e_{\mathrm{g}}$ orbital set. The occupation of these high-energy orbitals is the primary reason for this. The degeneracy of the $e_{\mathrm{g}}$ set is broken, the symmetry is decreased, and occupations at lower energy orbitals occur as the system becomes more stable with a lower energy configuration.
2. Hence, it is the correct option.

Therefore, the Jahn-Teller effect is not observed in high spin complexes of ${\mathrm{d}}^{10}$