Isovalent and mixed-valent molybdenum complexes containing Mo-V(mu-E)(mu-S-2)Mo-V/IV (E = O, S) core units

摘要

The reactions of Tp(iPr)MoO(SR)(NCMe) (Tp(iPr) = hydrotris(3-isopropylpyrazolyl)borate) with propylene sulfide in toluene result in the formation of the diamagnetic, isovalent Mo(V) complex, [Tp(iPr)Mo(V)O](2)(mu-S)(mu-S-2). This complex and its previously reported mu-oxo analog, [Tp(iPr)Mo(V)O](2)(mu-O)(mu-S-2), react with cobaltocene to produce one-electron-reduced, mixed-valent complexes, [CoCp2][{Tp(iPr)Mo(IV,V)O}(2)(mu-E) (mu-S-2)] (E = S or O, respectively). All complexes have been isolated and characterized by microanalysis, mass spectrometry, IR and H-1 NMR or EPR spectroscopies, and X-ray crystallography. Neutral [Tp(iPr)Mo(V)O] 2(mu-S)(mu-S-2) exhibits a pseudo-C-2 symmetric structure, with distorted octahedral anti oxo-Mo(IV) centers coordinated by Tp(iPr) and linked by mu-sulfido and mu-disulfido ligands. A similar structure is adopted by the anion in mixed-valent [CoCp2][{Tp(iPr)Mo(IV,V)O}(2)(mu-S)(mu-S-2)]; this compound adopts a hexagonal, supramolecular structure with columns of tight ion-pairs with (mu-S-2)center dot center dot center dot CoCp2+ interactions, interconnected through weaker (mu-S)center dot center dot center dot CoCp2+ 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.