Question

In octahedral ligand field which of the metal's d-orbitals will feel higher repulsion?

• A. $d_{xy},d_{yz},d_{zx}$
• B. $d_{x^2-y^2},d_{z^2}$
• C. $d_{xz},d_{yz},d_{z^2}$
• D. $d_{xy},d_{yz},d_{zx},d_{x^2-y^2},d_{z^2}$

Answer 1

The correct option is B $d_{x^2-y^2},d_{z^2}$

In a coordination entity with six ligands surrounding the metal atom/ion, there will be repulsion between ​electrons​ in metal’s ​d-orbitals and electrons (or negative charge) of the ligands.

In octahedral complex formation, ligands approach from/towards the axes.​ Thus, the orbitals present towards the axes will be repelled greater than the orbitals present between the axes.
The orbitals $d_{x^2-y^2}$ and $d_{z^2}$ lying along the axis and the lobes of orbitals $d_{xy},d_{yz}\text{and}{d}_{xz}$ are directed between the axis.

As a result, $d_{x^2-y^2}$ and $d_{z^2}$ orbitals energy are repelled more and increase in energy whereas energy of $d_{xy},d_{yz}\text{and}{d}_{xz}$ are decreased.

Hence, option (b) is correct.