Mono-oxo Bis(dithiolene) Mo(IV)/W(IV) Complexes as Building Blocks for Sulfide Bridged Bi- and Tri-Nuclear Complexes

A new electron precise, six-electron, sulfide-bicapped trinuclear cluster complex [Et4N]4[MoIV3(μ3-S)2(mnt)6] (1) has been synthesized, where each MoIV atom is seven coordinated. Identical reaction conditions yielded a dimeric complex, [PNP]2[WV2(μ2-S)2(mnt)4] (2) from the starting WIV analogue due to oxidation by sulfur formed by the auto-oxidation of H2S. Two stepwise reversible reductions and no oxidation of 2 as observed by cyclic voltammetry are correlated with the nonbonding nature of the lowest unoccupied molecular orbital and deeply buried highest occupied molecular orbital by theoretical calculations at the density-functional theory level.