Multiple active oxidants in cytochrome P-450 model oxidations

We report evidence for the existence of distinct active oxidizing species i n a cytochrome P-450 model system. Competitive oxidations of alkane substra tes were carried out using [5,10,15,20-tetrakis-(pentafluorophenyl)porphyri nato]iron(III) chloride (Fe(TPF5P)Cl) with various iodosylarenes as the oxy gen source. The oxidation rate ratios for each pair of substrates were foun d to differ when different iodosylarenes were employed as terminal oxidants . These competitive oxidation results unambiguously demonstrate that the ac tive oxidants generated from the various terminal oxidants are not the same . The influence of the oxygen donor on the selectivity requires that the do nor is involved in the product-determining step. We propose that the active oxidant is a complex between the catalyst and the terminal oxidant.