Kinetic and mechanistic studies of high-valent corrole-metal-oxo species; models for cytochromes P450

High-valent corrole-manganese(V)-oxo and corrole-iron(V)-oxo intermediates were studied by laser flash photolysis (LFP) methods. These intermediates were generated by laser irradiation (355 nm) of the corresponding corrole-metal(IV)-chlorate complexes. The kinetics of their self-decay reactions and their reactions with organic substrates were studied. The corrole ligands studied were 5,10,15- tris(pentafluorophenyl)corrole (TPFCH 3), 5,10,15-triphenylcorrole (TPCH3) and 5,15-bis (pentafluorophenyl)-10-(p-methoxyphenyl)corrole (BPFMCH3).;Contrary to what was expected in the (Cor)MnV(O) study, more electron-withdrawing corrole ligands produced (Cor)MnVO) species that were less reactive. In self-decay reactions and in reactions with substrates, the order of reactivity of (Cor)Mn V(O) was TPC > BPFMC > TPFC, which is inverted from that expected based on the electron-demand of the ligands. The rates of the reactions of (Cor)MnV(O) were increased with the concentration of the oxidant and other manganese species. The apparent rate constant for the reaction of (TPFC)Mn V(O) with triphenylamine showed fractional order with respect to the manganese-oxo-species. Most of our results could be explained by either one of the two following mechanisms: oxidation by (Cor)MnVI(O)(X), produced at low concentrations via disproportionation of (Cor)MnV(O), or oxidation by "free" (Cor)MnV(O) that equilibrates with inactive "sequestered" forms.;The highly reactive transients generated by LFP on (Cor)FeIV(ClO 3) are the most reactive corrole-metal-oxo species known to date. The order of reactivity is TPFC > BPFMC. Second-order rate constants of reactions of several substrates were studied. Representative rate constants for TPFC intermediate were kox = 7.4 x 10 3 M-1 s-1 for cyclohexene, kox = 5.9 x 103 M-1 s-1 for cyclooctene, and 5.7 x 102 M -1 s-1 for ethylbenzene. In a series of preparative scale experiments, the transient was shown to be a reactive iron-oxo intermediate which transfers oxygen to cyclooctene to generate cyclooctene epoxide. Rate constants of arene oxidation for the most reactive hydrogen were linearly correlated with bond dissociation energy (BDE) and ionization energy (IE) of the substrate. Based on the UV-visible spectrum and very high reactivity, this transient was tentatively assigned as a (Cor)FevV(O) species.