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 sul fides based on the 1,2-dithiole-3-thione subunit as found in the precu rsor dithiolate C3S52-. Tricyclic C6S8, 1, was obtained in high yield by thermal elimination of H2S from the dimercaptan beta-C3S5H2. A crys tallographic study confirmed a tricyclic structure of idealized D2h sy mmetry 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 fina l R and R(w) values were 0.036 and 0.042, respectively. The bicyclic c arbon sulfide C5S7, 3, was prepared from reduction of C4S6, 2, with Li BEt3H, followed by addition of thiophosgene. Oxidation of Cp2Ti(beta-C 3S5) or Zn(beta-C3S5)(2)2- with SO2Cl2 afforded [beta-C3S5]n, 4, an or ange insoluble solid. Degradation of [beta-C3S5]. with dimethyl acetyl enedicarboxylate (DMAD) afforded C3S5.2DMAD, 5, together with small am ounts of C3S5.3DMAD, 6. The single-crystal X-ray structure Of C3S5.-2D MAD revealed a folded 1,4-dithiin linked to a planar 1,3-dithiole. Cry stals 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 l east-squares refinement with anisotropic thermal parameters for all no n-hydrogen atoms converged at R = 0.036 and R(w) = 0.047. The DMAD tre atment 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 bi cyclic C4S6.DMAD, which can also be obtained via CP2Ti(C3S5.DMAD).