The nature of active species in catalytic systems based on non-heme iron complexes, hydrogen peroxide, and acetic acid for selective olefin epoxidation

The catalytic systems [(BPMEN)Fe-II(CH3CN)(2)](ClO4)(2)/H2O2/CH3OOH and [(TPA)Fe-II(CH3CN)(2)](ClO4)(2)/H2O2/CH3OOH, where BPMEN = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-diaminoethane and TPA = tris(2-pyridylmethyl)amine, provide selective olefin epoxidation. Proton NMR studies showed that the mononuclear iron(IV) oxo complexes [(L)Fe-IV=O](2+), with L = BPMEN or TPA, are present in the cited catalytic systems. These intermediates are the decomposition products of the acylperoxo complexes [(L)Fe-III-O3CCH3](2+). Such a complex was observed by the H-2 NMR technique at low temperatures. The [(L)Fe-IV=O](2+) and [(L)Fe-V=O](3+) oxo complexes are possible active species in the studied catalytic systems.