Question

The energies of $d_{xy}$ and $d_z^2$ orbitals in octahedral and tetrahedral transition metal complexes are such that

• A. $E\left(d_{xy}\right)>E\left(d_z^2\right)$ in both tetrahedral and octahedral complexes
• B. $E\left(d_{xy}\right)<E\left(d_z^2\right)$ in both tetrahedral and octahedral complexes
• C. $E\left(d_{xy}\right)<E\left(d_z^2\right)$ in tetrahedral but $E\left(d_{xy}\right)<E\left(d_z^2\right)$ in octahedral complexes
• D. $E\left(d_{xy}\right)<E\left(d_z^2\right)$ in tetrahedral but $E\left(d_{xy}\right)>E\left(d_z^2\right)$ in octahedral complexes

Answer 1

Answer: (C)

The five degenerate $d$-orbitals of the metal ion split into different sets of orbital having different energies in the presence of electrical field of ligand.
In octahedral metal complexes $d_{x^2-y^2}$ and $d_z^2$-orbitals point towards the axes along the direction of the ligand will experience more repulsion and will be raised in energy and the $d_{xy},d_{zx}$ and $d_{yz}$-orbitals are directed between the axes will be lowered in energy.
In tetrahedral metal complexes $d_{xy},d_{zx}$ and $d_{yz}$ experience more repulsion and have more energy than $d_{x^2-y^2}$ and $d_z^2$.