Aryl-substituted organomolybdenum(II) complexes as olefin epoxidation catalysts

The epoxidation of selected olefins with a benzyl-substituted organomolybdenum complex and its fluorinated counterpart is described. With hexafluorobenzene (HFB) as solvent, turnover frequencies (TOFs) of >15500 h^-1 are achieved in the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as the oxidant. The fluorinated complex, [CpMo(CO)₃BzF₅], proved to be superior to the non-fluorinated derivative in activity and selectivity with a variety of substrates. This can be explained via X-ray crystallography analysis and with the help of density functional theory (DFT) calculations. Besides, both compounds were applied in two-phase catalytic reactions. Recycling for multiple catalytic runs is achieved without a significant loss of activity.