Catalytic olefin epoxidation with a fluorinated organomolybdenum complex

Monomeric organomolybdenum carbonyl complexes of general formula [(η ⁵-C ₅R ₅)Mo(CO) ₃X] (R = H, CH ₃, CH ₂Ph; X = alkyl, halide) are known to be pre-catalysts for olefin epoxidation. In this work, the application of a fluorinated complex, [CpMo(CO) ₃CF ₃] (Cp = η ⁵-C ₅H ₅), 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(η ⁵-C ₅H ₄(CH(CH ₂) _n)-η ¹-CH)(CO) ₃] are known to deliver better performances in catalytic epoxidation reactions at room temperature. [CpMo(CO) ₃CF ₃] 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.