The reactions of [MoII2(OAc)4] (OAc-: acetato) with catecholato derivatives (R-Cat2-), possessing electrondonating t-Bu groups (3,6-DTBCat2-) or electron-withdrawing Br groups (Br4Cat2-), results in the formation of a mononuclear complex [Na(THF)6][MoV(3,6-DTBCat)3] (1) and a dinuclear complex either [Na6(Br4SQ)2][MoIV2(μ-O)2-(Br4Cat)4] or [Na6(Br4Cat)2][MoV2(μ-O)2(Br4Cat)4] (3). Complex 3 has a [Mo(μ-O)2Mo] core as part of a dimer of [O=Mom(Br4Cat)2]n- (m = IV or V, n = 2 or 1) moieties assembled in a head-to-tail arrangement, which has been structurally characterized as the a bis-μ-oxo molybdenum dinuclear complex containing catecholato ligands. The bond distance between the Mo atoms (2.4286(17) A˚) strongly suggests that a MoIV=MoIV or MoV-MoV bonding character exists in 3. Differences in the substituent groups on the catecholato ligand affect not only the product formed but also the react ivity of both complexes. Complex 3 shows O-atom abstract ion reactivity with dimethyl sulfoxide (DMSO) and forms di methyl sulfide (DMS). These results support a high oxophilicity of the Mo center in 3.
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