Developing Pathways to the Synthesis of Low-Valence Molybdenum Methoxides: Preparation, Characterization, and Redox Chemistry of Dimeric and Tetrameric Molybdenum Alkoxide Clusters

摘要

The rare Mo=Mo double-bonded dimeric alkoxide complex [Mo2Cl4(OCH3)(4)(CH3OH)(2)] (1) was prepared by the simple methanolysis reaction of [MoCl4(CH3CN)(2)]. It was shown that the dissolution of 1 in thf results in the formation of the [Mo2O2Cl4(OCH3)(2)(thf)(2)] (2) and [Mo2Cl4(OCH3)(4)(thf)(2)] (3) dimers. A novel tetranuclear 10e molybdenum cluster [Mo4Cl4O2(OCH3)(6)(CH3OH)(4)] (4) was synthesized by the spontaneous disproportionation of 1 in methanol. An alternative pathway to 4 based on the redox reaction of Mo3+ and Mo5+ compounds {in the form of [MoCl3(thf)(3)] and [Mo2Cl4(OCH3)(6)] (5), respectively} was proposed and realized. The redox behavior of 4 was investigated by means of cyclic voltammetry. It was demonstrated that 4 may undergo a reversible two-electron reduction process, which implies the retention of the {Mo-4} core, whereas the oxidation is irreversible, proceeding apparently with the destruction of the tetranuclear cluster core.