The Origin of the Unusual C_4ν Structure Predicted for SH₄

Abstract

Ab initio molecular orbital calculations have been performed on C_2v and C_4v isomers of SH₄, SF₄ and S(CH₃)₄ to investigate the origin of the different structures adopted by these molecules. We propose an electrostatic model similar in spirit to the VSEPR approach; this implies that the net charges on the ligands L in SL₄ compounds can control the geometry of these compounds. Steric factors may also be significant. Even though the net charges on hydrogen and on the CH₃ group are similar when these act as ligands towards sulfur, the carbon atom in the methyl group bears a substantial negative net charge, which has important structural consequences. Binding energies and structural parameters are presented for SH₄ which are obtained from more complete theoretical calculations than those previously reported.