A side-on Mn(III)-peroxo supported by a non-heme pentadentate N3Py2 ligand: Synthesis, characterization and reactivity studies

Abstract

Mononuclear manganese(III)-peroxo complex, [MnIII(N3Py2)(O2)]+ (1a) bearing a non-heme N,N'-dimethyl-N-(2-(methyl(pyridin-2-ylmethyl)amino)ethyl)-N'-(pyridin-2-ylmethyl)ethane-1,2-diamine (N3Py2) ligand was synthesized by the reaction of [Mn(N3Py2)(H2O)](ClO4)2 (1) with hydrogen peroxide and triethylamine in CH3CN at 25 degrees C. The reactivity of 1a in aldehyde deformylation using 2-phenyl propionaldehyde (2-PPA) was studied and the reaction kinetics was monitored by UV-visible spectroscopy. A kinetic isotope effect (KIE) = 1.7 was obtained in the reaction of 1a with 2-PPA and alpha-[D1]-PPA suggesting nucleophilic character of 1a. The activation parameters enthalpy change diesis and entropy change diesis were determined using Eyring plot while Ea was obtained from Arrhenius equation by performing the reaction between 288 to 303 K. Hammett constants (Sigma p) of para-substituted benzaldehydes p-X _ Ph _ CHO (X = Cl, F, H, Me) was linear with the slope (Rho) = 3.0. Computational study suggested that the side-on structure of 1a is more favored over the end-on structure and facilitates the reactivity of 1a.