A Side-On Mn(Iii)-Peroxo Supported By A Non-Heme Pentadentate N3py2 Ligand: Synthesis, Characterization And Reactivity Studies

A mononuclear manganese(iii)-peroxo complex [Mn-III(N3Py2)(O-2)](+) (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-[D-1]-PPA, suggesting nucleophilic character of 1a. The activation parameters Delta H-double dagger and Delta S-double dagger were determined using the Eyring plot while E-a was obtained from the Arrhenius equation by performing the reaction between 288 and 303 K. Hammett constants (sigma(p)) of para-substituted benzaldehydes p-X-Ph-CHO (X = Cl, F, H, and Me) were linear with a 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.