Page "Hypervalent molecule" Paragraph 26

In the 1950s molecular orbital treatment of hypervalent bonding was adduced to explain the molecular architecture.

According to MO theory, the central atom of penta-and hexacoordinated molecules would be sp < sup > 3 </ sup > d and sp < sup > 3 </ sup > d < sup > 2 </ sup > hybridized, which requires the promotion of central atom electrons to unoccupied d-orbitals.

However, advances in the study of ab initio calculations have revealed that the contribution of d-orbitals to hypervalent bonding is too small to describe the bonding properties, and this hybrid orbital description is now regarded as much less important.

It was shown that in the case of hexacoordinated SF < sub > 6 </ sub >, d-orbitals are not involved in S-F bond formation, but charge transfer between the sulfur and fluorine atoms and the apposite resonance structures were able to account for the hypervalency.