Substituent effects in second row molecules : Sulfur(II) compounds

Substituent effects arising from directly bonded groups in sulfur-containing compounds are investigated by molecular orbital calculations of relative energies. Interaction energies, basicities and acidities are obtained from calculations at the supplemented 4–3 IG and 6–3 IG basis set levels for substitution in the three series of sulfur compounds SX^-, SHX, and SH₂X⁺ with X = BH₂, CH₃, NH₂, OH, F and in the bisubstituted series SX₂ (X = CH₃, F). Donor-acceptor interactions are dominated by the σ-electrons and readily account for the data; substitution by BH₂ is an exception, requiring consideration of π-bonding, especially in the anion. Charge transfer, both to and from the second row element, is better tolerated by the sulfur-containing systems than by the corresponding oxygen compounds.