Chiral Cationic [Cp′Mo(CO)2(NCMe)]+ Species – Catalyst Precursors for Olefin Epoxidation with H2O2 and tert‐Butyl Hydroperoxide

摘要: A novel cyclopentadienyl ligand bearing a chiral oxazoline pendant group (Cpox) has been prepared. Its coordination to molybdenum and tungsten afforded optically pure (R)-CpoxM(η3-C3H5)(CO)2 (M = Mo, W) in which the fragment is not coordinated metal center. Reaction of (R)-CpoxMo(η3-C3H5)(CO)2 with tetrafluoroboric acid gives bidentate η5-cyclopentadienyloxazoline complex [CpoxMo(CO)2(NCMe)]BF4 through N-atom Their catalytic performance epoxidation cis-cyclooctene, (R)-limonene, trans-β-methylstyrene H2O2 tert-butyl hydroperoxide (TBHP) as oxidants studied. (R)-CpoxW(η3-C3H5)(CO)2 displayed high activity achieving quantitative conversion cyclooctene epoxide 2 h H2O2. [CpoxMo(CO)2(NCMe)]+ shown be an efficient catalyst TBHP H2O2, reaching conversions corresponding 30 min 11 h, respectively. ESI-MS studies reaction revealed situ formation peroxido [CpoxMo(O2)O]+ dioxido [CpoxMoO2]+ species, Further oxidation these complexes resulted loss cyclopentadienyloxazoline ligand. Based on spin trap experiments, involvement both carbon- oxygen-centred radicals olefin catalyzed by proved.