Methoxycarbonyl trifluoromethyl disulfide, CH3OC(O)SSCF3: synthesis, structure and conformational properties

Pure methoxycarbonyl trifluoromethyl disulfide, CH3OC(O)SSCF3, has been prepared quantitatively by the reaction of CH3OC(O)SCl and Hg(SCF3)(2). The conformational properties of the novel molecule have been studied by vibrational spectroscopy [IR(gas) and Raman(liquid)] and quantum chemical calculations (B3LYP and MP2 methods). The gaseous compound exhibits a conformational equilibrium at room temperature where the most stable form has C-1 symmetry with a synperiplanar (syn) orientation of the C=O double bond with respect to the S-S disulfide bond. A second form is observed in the gaseous IR spectra corresponding to a conformer with the carbonyl bond C=O in antiperiplanar (anti) position with respect to the S-S single bond. The structure of a single crystal of CH3OC(O) SSCF3 has been determined by X-ray diffraction analysis at low temperature using a miniature zone melting procedure. The crystalline solid (triclinic, P (1) over bar, a = 6.4698(5) angstrom, b = 9.0499(8) angstrom, c = 12.5700(11) angstrom, alpha = 97.219(6)degrees 1, beta = 93.131 (5)degrees, gamma = 96.888(5)degrees and Z = 4) consists exclusively of molecules with the synperiplanar conformation and the usual gauche orientation around the disulfide bond [phi(CS-SC) = 91.06(15)degrees] is adopted. The geometrical parameters agree with those obtained from quantum chemical calculations.