Model calculations on thiocarbonyl systems

Abstract

The potential surface for the valence tautomerism of 4-thioformyl-1,2-dithiole-3-thione (2) is investigated using the extended Hückel method. The different paths from one isomer to the other and individual aspects of the potential surface are discussed. It is found that (2) the energy difference between a structure of C_2v symmetry and C_s symmetry is ca. 35 kcal mol^–1 due to the non-linear arrangement of the four sulphur atoms. Other systems containing thiocarbonyl groups have been investigated with regard to possible valence tautomerism.