Isovalent and mixed-valent molybdenum complexes containing MoV(μ-E)(μ-S2)MoV/IV (E=O, S) core units

Abstract

The reactions of TpiPrMoO(SR)(NCMe) (TpiPr = hydrotris(3-isopropylpyrazolyl)borate) with propylene sulfide in toluene result in the formation of the diamagnetic, isovalent Mo(V) complex, [TpiPrMoVO]2(μ-S)(μ-S2). This complex and its previously reported μ-oxo analog, [TpiPrMoVO]2(μ-O)(μ-S2), react with cobaltocene to produce one-electron-reduced, mixed-valent complexes, [CoCp2][{TpiPrMoIV,VO}2(μ-E)(μ-S2)] (E = S or O, respectively). All complexes have been isolated and characterized by microanalysis, mass spectrometry, IR and 1H NMR or EPR spectroscopies, and X-ray crystallography. Neutral [TpiPrMoVO]2(μ-S)(μ-S2) exhibits a pseudo-C2 symmetric structure, with distorted octahedral anti oxo-Mo(IV) centers coordinated by TpiPr and linked by μ-sulfido and μ-disulfido ligands. A similar structure is adopted by the anion in mixed-valent [CoCp2][{TpiPrMoIV,VO}2(μ-S)(μ-S2)]; this compound adopts a hexagonal, supramolecular structure with columns of tight ion-pairs with View the MathML source interactions, interconnected through weaker View the MathML source contacts to three neighboring columns. The structure contains large interstitial voids filled with lattice solvent molecules. EPR investigation of the mixed-valent complexes gave rise to unusually broad signals with no evident hyperfine splitting. The synthesis and characterization of a number of cis-dioxo-Mo(VI) precursors are also reported.