Formation of Mono(dithiolene)−Thiocarboxamido Complexes in Reactions of Thio(dithiocarbamato)−Mo/W Complexes and Dimethyl Acetylenedicarboxylate

Reactions of Tp*MS(S2CNEt2) with dimethyl acetylenedicarboxylate in dichloromethane produce olive green/black Tp*M{S2C2(CO2Me)2}(SCNEt2-κ2 S,C) (M = Mo (1), W (2); Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate). The seven-coordinate complexes exhibit pseudo-octahedral (1) and distorted pentagonal bipyramidal (2) coordination spheres comprised of tridentate fac-Tp*, bidentate dithiolene, and thiocarboxamido-κ2 S,C ligands. In the solid state, molecules of 1 exhibit pseudo-C s symmetry, with the thiocarboxamide NEt2 group in a cleft in the Tp* ligand. Molecules of 2 have C 1 symmetry in the solid state; here, the thiocarboxamide unit is orientated along one of the W−S(dithiolene) bonds with its NEt2 group projecting away from the Tp* ligand. Both complexes possess effective C s symmetry in solution. Reaction of Tp*MoI(CO)3 with AgS2CNEt2 affords olive green Tp*Mo(S2CNEt2)(CO)2 (3), which reacts with propylene sulfide in a new synthesis for Tp*MoS(S2CNEt2), the starting material for 1. Complex 3 exhibits a distorted pentagonal bipyramidal structure, the axial sites being defined by a Tp* nitrogen atom and a carbonyl ligand, the pentagonal plane by the remaining nitrogen and carbonyl donors and the two sulfur atoms of the bidentate dithiocarbamate ligand.