STRUCTURES AND CONFORMATIONS OF CF3SC(O)F AND CF3SC(O)CL - GAS-PHASE ELECTRON-DIFFRACTION, VIBRATIONAL ANALYSIS, AND THEORETICAL CALCULATIONS

The geometric structures and conformational properties of (fluorocarbo nyl)trifluoromethylsulfane, CF3SC(O)F, and (chlorocarbonyl)trifluorome thylsulfane, CF3SC(O)Cl, were determined by gas electron diffraction ( GED), vibrational spectroscopy (IR(matrix)), and theoretical calculati ons (HF/3-21G, HF/6-31G*, MP2/6-31G* ab initio, and BPW91/6-31G*, B3P W91/6-31G density functional methods). For CF3SC(O)F a mixture of pla nar syn and anti conformers occurs with Delta G(o)(GED) = G(o)(anti) - G(o)(syn) = 1.3(4) kcal mol(-1) and Delta H-o(IR) = H-o(anti) - H-o(s yn) = 1.43(12) kcal mol(-1). Only the planar syn form is obtained in t he case of CF3SC(O)Cl. All theoretical approaches reproduce the geomet ric parameters and conformational properties of both compounds very we ll. The predicted energy differences Delta E = E(anti) - E(syn) vary f rom 0.98 to 1.24 kcal mol(-1) for CF3SC(O)F and from 2.96 to 3.69 kcal mol(-1) for CF3SC(O)Cl.