| Abstract
| - [Mo(η3-allyl)X(CO)2(N−N)] complexes (N−N = bidentate ligand) catalyze the epoxidation of olefins using tert-butyl hydroperoxide as oxidant, with 100% selectivity toward epoxide formation. Turnover frequencies compare with those of related molybdenum catalysts, and they exhibit similar olefin conversions in consecutive catalytic runs.
- New Mo(II) diimine derivatives of [Mo(η3-allyl)X(CO)2(CH3CN)2] (allyl = C3H5 and C5H5O; X =Cl, Br) were prepared, and [Mo(η3-C3H5)Cl(CO)2(BIAN)] (BIAN = 1,4-(4-chloro)phenyl-2,3-naphthalenediazabutadiene) (7) was structurally characterized by single-crystal X-ray diffraction. This complexadopted an equatorial−axial arrangement of the bidentate ligand (axial isomer), in contrast with theprecursors, found as the equatorial isomer in the solid and fluxional in solution. The new complexes ofthe type [Mo(η3-allyl)X(CO)2(N−N)] (N−N is a bidentate chelating dinitrogen ligand) were tested forthe catalytic epoxidation of cyclooctene using tert-butyl hydroperoxide as oxidant. All catalytic systemswere 100% selective toward epoxide formation. While their turnover frequencies paralleled those ofrelated Mo(II) carbonyl compounds or Mo(VI) compounds bearing similar N-donor ligands, they exhibitedsimilar olefin conversions in consecutive catalytic runs. The acetonitrile precursors were generally moreactive than the diimine complexes, and the chloro derivatives more active than the bromo ones. Combinedvibrational and NMR spectroscopy and computational studies (DFT) were used to investigate the natureof the molybdenum species formed in the catalytic system with [Mo(η3-C3H5)Cl(CO)2{1,4-(2,6-dimethyl)phenyl-2,3-dimethyldiazabutadiene}] (4) and to propose that the resulting species may be dimeric bearingoxide bridges.
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