The synthesis and structures of two types of molecules are presented: [(MO3-nSn)-O-VI(OSiR2R')](1-) (M = Mo, n = 0-3; M = W, n = 3) and [(MO2)-O-VI(OSiR2R')(bdt)](1-) (M = Mo, W; bdt = benzene-1,2-dithiolate). For both types, R2R' are Me-3, Pr-3(i), Ph-3, Me2But and Ph2But. The complete series of oxo/sulfido/silyloxo molybdenum complexes has been prepared. Complexes with n = 0 are readily prepared by the silylation of Ag2MoO4 and sustain mono- or disulfidation with Ph3SiSH to form a species with n = 1 and n = 2, respectively. Complexes with n = 3 are accessible by the silylation of [MOS3](2-). Structures of the representative series members [MoO3(OSiPh2But)](1-), [MoO2S(OSiPh3)](1-), [MoOS2(OSiPr3i)](1-), [MoS3(OSiPh2But)](1-), and also [WS3(OSiMe2But)](1-), all with tetrahedral stereochemistry, are presented. Benzene-1,2-dithiolate complexes are prepared by the reaction of [MoO3(OSiR2R')](1-) with the dithiol or by the silylation of previously reported [MO3(bdt)](2-). The structures of [MoO2(OSiPh2But)(bdt)](1-) and [WO2(OSiPr3i)(bdt)](1-) conform to square-pyramidal stereochemistry with an oxo ligand in the apical position. The role of these complexes in the preparation of site analogues of the xanthine oxidoreductase enzyme family is noted. The sulfidation reactions reported here point to the utility of Ph3SiSH and (Pr3SiSH)-Si-i as reagents for Mo-VI-based oxo-for-sulfido conversions.