SYNTHESIS, STRUCTURE, AND CHARACTERIZATION OF BIS(DIETHYLDITHIOCARBAMATO)(DIETHYLTHIOCARBAMYL)SULFIDONIOBIUM(V) AND ITS TANTALUM ANALOG

The compounds MS(eta-2-SCNEt2)(eta-2-S2CNEt2)2 (M = niobium or tantalum) have been prepared from the reaction of NaS2CNEt2 with M2Cl6(SC4H8)3. These new compounds were characterized using spectroscopic methods and X-ray crystallography. NbS(SCNEt2)(S2CNEt2)2.1/4C6H6 crystallizes in the triclinic space group, P1BAR, with cell parameters of a = 10.390 (4) angstrom, b = 14.002 (3) angstrom, c = 18.314 (11) angstrom, alpha = 104.39 (4)-degrees, beta = 93.13 (4)-degrees, gamma = 90.11 (3)-degrees, V = 2576 (2) angstrom3, and Z = 4. The coordination sphere of the metal(V) atom consists of a lone sulfur atom, two chelating dithiocarbamate ligands, and one thiocarbamyl ligand bound through both the carbon and the sulfur atoms. The resulting structure is a seven-coordinate pentagonal bipyramid having the lone sulfur atom and a sulfur from one of the dithiocarbamate ligands occupying the polar positions. The formation of a sulfur ligand and thiocarbamyl ligand, SCNEt2-, corresponds to the oxidative addition of one C-S bond to the metal(III) center with concomitant cleavage of the dimer. A dimeric compound with bridging tridentate dithiocarbamate ligands is proposed as a necessary intermediate for the oxidative addition reaction to occur.