A Mechanistic Spectrum of O−H Bond Cleavage Observed for Reactions of Phenols with a Manganese Superoxo Complex

Abstract

Reaction of a rare and well‐characterized MnIII‐superoxo species, Mn(BDPBrP)(O2•) (1, H2BDPBrP = 2,6‐bis((2‐(S)‐di(4‐bromo)phenylhydroxylmethyl‐1‐pyrrolidinyl)methyl)pyridine), with 4‐dimethylaminophenol at −80 °C proceeds via concerted proton electron transfer (CPET) to produce a MnIII‐hydroperoxo complex, Mn(BDPBrP)(OOH) (2), alongside 4‐dimethylaminophenoxy radical; whereas, upon treatment with 4‐nitrophenol, complex 1 undergoes a proton transfer process to afford a MnIV‐hydroperoxo complex, [Mn(BDPBrP)(OOH)]+ (3). Intriguingly, the reactions of 1 with 4‐chlorophenol and 4‐methoxyphenol follow two routes of CPET and sequential proton and electron transfer to furnish complex 2 in the end. UV‐vis and EPR spectroscopic studies coupled with DFT calculations provided support for this wide mechanistic spectrum of activating various phenol O‐H bonds by a single MnIII‐superoxo complex, 1.