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.