SCF-Xα Scattered-Wave Studies on Bonding and Ionization Potentials. 2. Higher Valence State Sulfur Compounds

The nature of the bonding in hypervalent molecules is examined for the series SX₆ (X = F, Cl, H) as well as for SF₄ and SOF₄ by means of SCF-Xα scattered-wave calculations. We refine our method of “atoms-in-molecule” population analysis to distinguish different partial wave contributions in the individual atomic regions. For the SX₆ series, we discuss the correlation of electronegativity of the ligands (bond polarity) and the existence of these compounds. The bonding in SF₆ is affected in a different way by the ligand s orbitals than in SCl₆, a factor not included in the original theory of hypervalency. A detailed analysis of the nature of the bonding in SF₆ is made by using both the partial wave population analysis and orbital contour maps. A great similarity between the electronic structure of SF₄, SOF₄, and SF₆ is found which does not justify the usual distinction between hypervalent I (SF₄) and hypervalent II (SOF₄, SF₆) bonding. We find in agreement with experiment that the axial fluorine ligands in SF₄ have smaller F Is ionization energies than the equatorial ligands. The first ionization potential of SOF₄ is smaller than that of SF₄ (14.5 vs. 16.2 eV).