Non-empirical calculations of the nature of the bonding in thiophen, thiophen S-oxide, and thiophen SS-dioxide

Abstract

LCGO Calculations are reported for the title compounds. A not-planar structure similar to that recently reported for 1-benzylphosphole is more stable than the planar form for the S-oxide. The electron distributions are interpreted in teRms of localised orbitals, and it is clear that the 3d orbitals play a significant part in the bonding of the S-oxide and SS-dioxide. Neither of the latter compounds show evidence of aromatic character; the overlap populations show a progressive increase in diene character across the series pyrrole, thiophen, its S-oxide, and its SS-dioxide, conssitent with the ready dimerisation of the latter pair.