NEW CARBON SULFIDES BASED ON 4,5-DIMERCAPTO-1,2-DITHIOLE-3-THIONE (BETA-C3S(5)2-) - [C3S5]N, C6S8, AND C5S7

This investigation centers on the preparation of new binary carbon sulfides based on the 1,2-dithiole-3-thione subunit as found in the precursor dithiolate C3S52-. Tricyclic C6S8, 1, was obtained in high yield by thermal elimination of H2S from the dimercaptan beta-C3S5H2. A crystallographic study confirmed a tricyclic structure of idealized D2h symmetry containing an unusual planar 1,4-dithiin unit. The crystals of 1 are monoclinic, space group P2(1)/c, with a = 8.046(2), b = 9.797(3), c = 13.818(4) angstrom, v = 1048.3(9) angstrom3, and Z = 4. The final R and R(w) values were 0.036 and 0.042, respectively. The bicyclic carbon sulfide C5S7, 3, was prepared from reduction of C4S6, 2, with LiBEt3H, followed by addition of thiophosgene. Oxidation of Cp2Ti(beta-C3S5) or Zn(beta-C3S5)(2)2- with SO2Cl2 afforded [beta-C3S5]n, 4, an orange insoluble solid. Degradation of [beta-C3S5]. with dimethyl acetylenedicarboxylate (DMAD) afforded C3S5.2DMAD, 5, together with small amounts of C3S5.3DMAD, 6. The single-crystal X-ray structure Of C3S5.-2DMAD revealed a folded 1,4-dithiin linked to a planar 1,3-dithiole. Crystals of 5 are monoclinic, space group Cc, with a = 18.760(4), b = 13.664(3), c = 7.880(2) angstrom, V = 1957(2) angstrom3, and Z = 4. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.036 and R(w) = 0.047. The DMAD treatment proceeds in a similar manner with [M(beta-C3S5)2]2- (M = Zn, Ni) to yield [M(C3S5.DMAD)2]2-. The C3S5.DMAD ligand can subsequently be removed from the zinc complex by reaction with thiophosgene giving bicyclic C4S6.DMAD, which can also be obtained via CP2Ti(C3S5.DMAD).