A Mn(iv)–peroxo complex in the reactions with proton donors

Abstract

Protons play an important role in promoting O–O or M–O bond cleavage of metal–peroxo complexes. Treatment of side-on O₂-bound [PPN][Mn^IV(^TMSPS3)(O₂)] (1, PPN = bis(triphenylphosphine)iminium and ^TMSPS3H₃ = 2,2′,2′′-trimercapto-3,3′,3′′-tris(trimethylsilyl)triphenylphosphine) with perchloric acid (HClO₄) in the presence of PR₃ (R = phenyl or p-tolyl) results in the formation of neutral five-coordinate Mn^III(OPR₃)(^TMSPS3) complexes (R = phenyl, 2a; p-tolyl, 2b), which are confirmed by X-ray crystallography. Isotope labelling experiments demonstrate that the oxygen atom in the phosphine oxide product derives from the peroxo ligand of 1. Reactions of 1 with weak proton donors, such as phenylthiol, phenol, substituted phenol and methanol, are also investigated to explore the reactivity of the Mn^IV–peroxo complex, leading to the isolation of a series of five-coordinate [Mn^III(L)(^TMSPS3)]⁻ complexes (L = phenylthiolate, phenolate or methoxide). Mechanistic aspects of the reactions of the Mn^IV–peroxo complex with proton donors are discussed as well.