Non-Binding Orbitals, s-Bonding and d-Orbital Participation in Hypervalent Molecules.

The role of non-bonding orbitals in a simple molecular-orbital scheme for hypervalent molecules is discussed. It is shown that the quantitative amount of s-bonding, which occurs only for molecules formed from atoms in their highest valences, is most important in determining the stability of the molecule. The amount of d-orbital participation in molecules such as PF5 and SF6 is seen to make a contribution to the energy that is smaller than the contribution due to electron correlation. Author