Can Manganese(III)-Iodosylarene Act as an Oxidant Alongside High-Valent Manganese(V)-Oxo Complexes?

Metalloenzymes often utilize a high-valent metal-oxo species in their catalytic cycle that is formed through a combination of reduction/proton transfer steps from O-2. In biomimetic chemistry, by contrast, the use of molecular oxygen is challenging and instead addition of iodosylarenes as terminal oxidants generates these high-valent metal-oxo intermediates. There has been controversy in the literature for many years, whether the iodosylarene (or one of its side-products in a reaction with a metal center) can act as an active oxidant. Herein, we present a comprehensive theoretical study on the thioanisole oxidation by a range of possible oxidants originating from a reaction mixture of a Mn(III) complex with iodosylbenzene. We show here that actually there are multiple isomeric iodosylarene complexes in solution and a number of those react with substrates with rate-determining barriers at par with high-valent metal-oxo species. In particular, the [Mn-III(PhIO)], [Mn-V(O)(PhIO)] and [Mn-IV(O)-I(Ph)-O-center dot] complexes are identified as competitive oxidants and as such care should be taken with interpreting experimental rate constants.