To regulate the reactivity of dithiolene dioxomolybdenum(VI) complexes, two systems were studied : (1) chelate recognition with a diamide additive, 1,3-bis(isobutyrylamino)benzene (1); (2) a dithiolene complex with four amide substituents, (n-Pr4N)(2)[(MoO)-O-IV{S2C2(CONH2)(2)}(2)]. 0.5(i-PrOH). DMF (2) (S2C2(CONH2)(2) = 1,2-dicarbamoylethylene- 1,2-dithiolate). Both amide compounds, the additive 1 and the complex 2, were designed to form NH ... S and/or NH ... O hydrogen bonding with thiolate ligands in ((MoO)-O-IV)(2+) and ((MoO)-O-IV)(2+) complexes. Titration analyses indicate the presence of a 1:1 complex in CH2Cl2 solution. This association causes changes in solubility and reactivity of the molybdenum complexes. When the additive was mixed with a DMSO-do solution of (NEt(4))(2)[(MoO)-O-IV{S(2)C2(COOMe)(2)}(2)] (3) (S2C2(COOMe)(2) = 1,2-di(methoxycarbonyl)ethylene-1,2-dithiolate), the rate of reduction of Me(3)NO was increased by a factor of 6. An acceleration was also observed for compound 2. It appeares that NH ... S hydogen bonding is modulating the system.