Ethyltrioxorhenium – Catalytic application and decomposition pathways

Despite its sensitivity, ethyltrioxorhenium (ETO) is applicable as catalyst in the epoxidation of olefins using either tert-butylhydroperoxide (TBHP) or hydrogen peroxide as oxidants. Conversions of approximately 80% with only epoxide being formed and a turnover frequency (TOF) of up to 1200 h−1 can be achieved with TBHP in 1,1,1,3,3,3-hexafluroroisopropanol (HFI). As proven for its more stable congener MTO, the active species is highly likely an alkyl peroxo species, as shown by 17O-NMR experiments. Experimental and theoretical studies on the decomposition mechanism of ETO in diluted polar solvents reveal that the degradation pathway proceeds equally via β-hydrogen elimination and radical decomposition.