Cooperative Pull and Push Effects on the O−O Bond Cleavage in Acylperoxo Complexes of [(Salen)MnIIIL]: Ensuring Formation of Manganese(V) Oxo Species

Abstract

The acidity (pull) and the axial ligand (push) effects on the O-O bond cleavage in the [(Salen)Mn(III)(RCO(3))L] acylperoxo complexes, with model L = none, NH(3), and HCO(2)(-) (1), have been studied with B3LYP density functional calculations. The acidic conditions have been mimicked by explicit protonation of 1 to afford a variety of [(Salen)Mn(III)(RCO(3)H)L] (2) and [(SalenH)Mn(III)(RCO(3))L] (3) complexes in ground quintet states. The protonation assists the O-O bond heterolysis, thus primarily forming highly reactive Mn(V)(O) species, and consequently suppresses formation of the less reactive Mn(IV)(O) species through homolytic channel described earlier in 1 [Khavrutskii, I. V.; Rahim, R. R.; Musaev, D. G.; Morokuma, K. J. Phys. Chem. B 2004, 108, 3845-3854]. In addition to the qualitative change of the O-O bond cleavage mode, the protonation affects the rate of the O-O bond cleavage. Therefore, varying the acidity of the reaction media helps control the O-O bond cleavage mode and rate.