Association of Oxo−Molybdenum Dithiolene Complexes with a Multiamide Additive and Its Influence on the Ease of O-Atom Transfer

Abstract

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-Pr(4)N)(2)[Mo(IV)O{S(2)C(2)(CONH(2))(2)}(2)].0.5(i-PrOH).DMF (2) (S(2)C(2)(CONH(2))(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 (Mo(VI)O(2))(2+) and (Mo(IV)O)(2+) complexes. Titration analyses indicate the presence of a 1:1 complex in CH(2)Cl(2) solution. This association causes changes in solubility and reactivity of the molybdenum complexes. When the additive was mixed with a DMSO-d(6) solution of (NEt(4))(2)[Mo(IV)O{S(2)C(2)(COOMe)(2)}(2)] (3) (S(2)C(2)(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.