Protonation of [(Me3tacn)MoO3] with one or two equivalents of strong proton acid afforded mono‐protonated complex [(Me3tacn)MoVIO2(OH)](CF3SO3) and bi‐protonated complex [(Me3tacn)MoVIO(OH)2](PF6)2, respectively. Sulfidation with iPr2NCS2Na or CS2 in acetonitrile, followed by in situ protonation of [(Me3tacn)MO3] (M=Mo, W), produced two monomeric complexes [(Me3tacn)MoVIO2S] ⋅ (iPr2NH2) ⋅ (PF6) ⋅ CH2Cl2 and [(Me3tacn)WVIO2S], and two dimeric complexes [(Me3tacn)MoVO(μ‐S)2MoVO(κ2‐S2C=O)] ⋅ CH3CN and [(Me3tacn)MoIVO]2(μ‐O)(μ‐S2) ⋅ 2DMF. The crystal structures of the two protonated molybdenum(VI) complexes and the four oxo‐sulfido molybdenum/tungsten complexes have been determined. Moreover, the complexes have been characterized by infrared, Raman, fluorescence and UV‐vis spectroscopies. (Me3tacn=1,4,7‐trimethyl‐1,4,7‐triazacyclonane).