Structural variation in diorganotin dimethylxanthates, R2Sn(S2COMe)(2): A combined crystallographic and theoretical investigation

The crystal and molecular structures of three R2Sn(S2COMe)(2) compounds hav e been determined and show that the tin atom in each case exists in a disto rted trapezoidal bipyramidal geometry with the tin-bound organo substituent s lying over the longer edge of the trapezoidal plane. For Me2Sn(S2COMe)(2) , one of the xanthate ligands, coordinates via both sulfur atoms (S-,S- che lation) but the other uses one sulfur and the oxygen atom in coordination t o tin (S-,O- chelation). More conventional geometries, with S-,S- chelation only, are found for Ph(Me)Sn(S2COMe)(2) and Ph2Sn(S2COMe)(2). Theoretical predictions of the isolated molecular structures have been calculated using ab initio and density functional theories (all with the 3-21G** basis set) and reveal a different arrangement of the ligand donor set for each compou nd, i.e., one featuring both ligands with S-,O- chelation, Differences betw een the single-molecule and solid-state structures are ascribed to the infl uence of intermolecular interactions on the molecular geometries in the sol id state.