Question

What is crystal field splitting energy? How does the magnitude of$Δo$ decide the actual configuration of d-orbitals in a coordination entity?

Answer 1

The degenerate d-orbitals (in a spherical field environment) split into two levels i.e., $e_g$ and $t_{2g}$ in the presence of ligands. The splitting of the degenerate levels due to the presence of ligands is called the crystal-field splitting while the energy difference between the two levels ($e_g$ and $t_{2g}$) is called the crystal-field splitting energy. It is denoted by $Δo$. After the orbitals have split, the filling of the electrons takes place. After 1 electron (each) has been filled in the three $t_{2g}$orbitals, the filling of the fourth electron takes place in two ways. It can enter the $e_g$ orbital (giving rise to t2g 3 eg 1 like electronic configuration) or the pairing of the electrons can take place in the $t_{2g}$ orbitals (giving rise to $t_{2g}$ 4 $e_g$ 0 like electronic configuration). If the Δo value of a ligand is less than the pairing energy $(P)$, then the electrons enter the egorbital. On the other hand, if the $Δo$ value of a ligand is more than the pairing energy $(P)$, then the electrons enter the $t_{2g}$orbital.