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 (CH 3 CN) 2 ](ClO 4 ) 2 /H 2 O 2 /CH 3 OOH and [(TPA)Fe II (CH 3 CN) 2 ](ClO 4 ) 2 /H 2 O 2 /CH 3 OOH, 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 -O 3 CCH 3 ] 2+ . Such a complex was observed by the 2 H 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.