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 O-2-bound [PPN][Mn-IV((TMS)PS3)(O-2)] (1, PPN = bis(triphenylphosphine)iminium and (TMS)PS3H(3) = 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)((TMS)PS3) 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)((TMS)PS3)](-) complexes (L = phenylthiolate, phenolate or methoxide). Mechanistic aspects of the reactions of the Mn-IV-peroxo complex with proton donors are discussed as well.