Synthetic models leading to oxosulfidotungsten(VI) groups and dithiolene chelate rings have been investigated. The heterogeneous reaction systems [WO4-nSn](2-)/2Ph(3)SiCl/Me(4)phen (n = 0-2) in acetonitrile afford the complexes [WQ(2)(OSiPh3)(2)(Mejphen)] (1-3) in the indicated yields containing the groups (WO2)-O-VI (1; 86%), (WOS)-O-VI (2; 45%), and (WS2)-S-VI (3; 83%). In the crystalline state these complexes have imposed C-2 symmetry, with cis-oxo/sulfido and trans-silyloxide ligands. H-1 NMR spectra indicate that this stereochemistry is retained in solution. The colors of 2 (yellow, 367 nm) and 3 (orange, 451 nm) arise from LMCT absorptions at the indicated wavelengths. These results demonstrate that the silylation procedure previously introduced for the preparation of molecules with the (MoOS)-O-VI group (Thapper, et al. Inorg. Chem. 1999, 38, 4104) extends to tungsten. Methods for the formation of dithiolene chelate rings MS2C2R2 in reactions with sulfide-bound M = Mo or W precursors are summarized. In a known reaction type, 3 and activated acetylenes rapidly form [W-IV(OSiPh3)(2)(Me(4)phen)(S2C2R2)] (R = CO2Me, 4, 83%, and Ph, 5, 98%). In a new reaction type not requiring the isolation of an intermediate, the systems [MO2S2](2-)/2Ph(3)SiCl/Me(4)phen/PhC=CPh in acetonitrile afford 5 (68%) and [Mo-IV(OSiPh3)(2)(Me(4)phen)(S2C2Ph2)] (6; 61%). Complexes 5 and 6 are isostructural, maintain the trans-silyloxide stereochemistry, and exhibit chelate ring dimensions indicative of ene-1,2-dithiolate coordination. Reductions in the -1.4 to -1.7 V range are described as metal-centered. It remains to be seen whether the oxo/sulfidotungsten(VI) groups in 1-3 eventuate in the active sites of tungstoenzymes. (Me4phen = 3,4,7,8-tetramethyl-1,10-phenanthroline).