Catalytic olefin epoxidation with a fluorinated organomolybdenum complex

Monomeric organomolybdenum carbonyl complexes of general formula [(η5-C5R5)Mo(CO)3X] (R = H, CH3, CH2Ph; X = alkyl, halide) are known to be pre-catalysts for olefin epoxidation. In this work, the application of a fluorinated complex, [CpMo(CO)3CF3] (Cp = η5-C5H5), is reported. With hexafluoroisopropanol as a solvent, a turnover frequency (TOF) of >6300 h−1 was achieved in the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as oxidant. So far, only ansa compounds of formula [Mo(η5-C5H4(CH(CH2)n)-η1-CH)(CO)3] are known to deliver better performances in catalytic epoxidation reactions at room temperature. [CpMo(CO)3CF3] was also applied in 2-phase catalytic epoxidation reactions. The high stability of the oxidised species allows catalyst recycling for multiple catalytic runs without significant loss of activity. Besides, the fluorinated complex enables – at this stage preliminary – mechanistic 19F NMR studies, indicating the nature of the catalytically active Mo-species, which has been an unresolved subject for some time.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (166 K)Download as PowerPoint slideHighlights► [CpMo(CO)3CF3] acts as a pre-catalyst of the epoxidation of olefins. ► The performance of [CpMo(CO)3CF3] is compared to [CpMo(CO)3CH3]. ► Fluorinated solvents activate TBHP, improving of the catalyst performance. ► Several homogeneous reaction media, including an ionic liquid, were studied. ► The stability of the oxidised species allows catalyst recycling.