Reactions of Tp(*)MS(S2CNEt2) with dimethyl acetylenedicarboxylate in dichloromethane produce olive green/black Tp(*)M {S2C2(CO2Me)(2)} (SCNEt2-kappa(2)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-kappa(2)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, 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, symmetry in solution. Reaction of Tp(*)Mol(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.