In the field of biomimetic catalysis, a plethora of transition metal complexes, specifically metalloporphyrin and metallosalens, have been synthesized to mirror the oxidative capability of heme-containing enzymes found in Nature. Most notably, cytochrome P450 enzymes bearing an iron protoporphyrin IX active site can efficiently assemble oxidized organic substrates with superior regio- and stereoselectivity. The principal oxidants involved with metalloporphyrin-catalyzed reactions are high-valent metal oxo species that can transfer oxo ligands to an organic reductant in a process referred to as oxygen atom transfer (OAT). In this presentation, a chemical pathway using iodobenzene diacetate was deployed to generate reactive manganese(IV)-oxo and chromium(V)-oxo intermediates, i.e. [MnIV(Por)O] (Por = porphyrin), [CrV(salen)O] (salen = (R,R)-(−)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine), and [MnV(salen)O]. By developing a promising photochemical approach, the same [MnIV(Por)O], [CrV(salen)O], and [MnV(salen)O] transients were also generated permitting direct kinetic studies of oxidation reactions in real-time with impressive temporal resolution. Comprehensive kinetic studies of OAT reactions through chemically generated metal-oxo intermediates were conducted, illuminating mechanistic interpretations of the oxidation routes where physical intermediates are not spectroscopically detectable.

Oxidation kinetic studies and photochemical production of high-valent manganese(IV)-oxo porphyrins, chromium(V)-oxo salens, and manganese(V)-oxo salens

ACS Spring Meeting 2021

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