Formation, Characterization, and Reactivity of the Oxene Adduct of iron(III) Perchlorate in Acetonitrile. Model for the Reactive Intermediate of Cytochrome P-450

Article abstract of DOI:10.1021/ja00216a020

Combination of iron(III) perchlorate with pentafluoroiodosobenzene, m-chloroperbenzoic acid, or ozone in acetonitrile at -35 deg C yields a green porphyrin-oxene adduct.This species, which has been characterized by spectroscopic, magnetic, and electrochemical methods, cleanly and stereospecifically epoxidizes olefins (>99percent exo-norbornene oxide).The reaction chemistry and electronic characterization of the adduct are consistent with an oxygen atom covalently bound to an iron(II)-porphyrin radical center (Por^.-)Fe^II(O)⁺>.The latter has the spectral, magnetic, and redox characteristics of compound I of horseradish peroxidase (HRP) and the selective stereospecific oxygenase character of the reactive intermediate for cytochrome P-450.Reduction of the green species by one electron equivalent yields a red species, PorFe^II(O), which has the spectral characteristics and reactivity of compound II of HRP.The iron(III)-porphyrin is an efficient catalyst for (a) the stereospecific epoxidation of olefins and (b) the oxidative cleavage of α-diols by F5PhIO and m-ClPhC(O)OOH; with H2O2, there is extensive attack on the porphyrin ring and no significant reaction with olefins or α-diols.