Mimicking Elementary Reactions of Manganese Lipoxygenase Using Mn-hydroxo and Mn-alkylperoxo Complexes

Manganese lipoxygenase (MnLOX) is an enzyme that converts polyunsaturated fatty acids to alkyl hydroperoxides. In proposed mechanisms for this enzyme, the transfer of a hydrogen atom from a substrate C-H bond to an active-site MnIII-hydroxo center initiates substrate oxidation. In some proposed mechanisms, the active-site MnIII-hydroxo complex is regenerated by the reaction of a MnIII-alkylperoxo intermediate with water by a ligand substitution reaction. In a recent study, we described a pair of MnIII-hydroxo and MnIII-alkylperoxo complexes supported by the same amide-containing pentadentate ligand (6Medpaq). In this present work, we describe the reaction of the MnIII-hydroxo unit in C-H and O-H bond oxidation processes, thus mimicking one of the elementary reactions of the MnLOX enzyme. An analysis of kinetic data shows that the MnIII-hydroxo complex [MnIII(OH)(6Medpaq)]+ oxidizes TEMPOH (2,2′-6,6′-tetramethylpiperidine-1-ol) faster than the majority of previously reported MnIII-hydroxo complexes. Using a combination of cyclic voltammetry and electronic structure computations, we demonstrate that the weak MnIII-N(pyridine) bonds lead to a higher MnIII/II reduction potential, increasing the driving force for substrate oxidation reactions and accounting for the faster reaction rate. In addition, we demonstrate that the MnIII-alkylperoxo complex [MnIII(OOtBu)(6Medpaq)]+ reacts with water to obtain the corresponding MnIII-hydroxo species, thus mimicking the ligand substitution step proposed for MnLOX.

Activation of ammonia and hydrazine by electron rich Fe(ii) complexes supported by a dianionic pentadentate ligand platform through a common terminal Fe(iii) amido intermediate

Synopsis: a highly reactive Fe(iii)–NH2 complex is generated via activation of ammonia or hydrazine in reactions of relevance to fundamental steps in ammonia oxidation processes mediated by an abundant, first row transition metal.

A DFT study on the C–H oxidation reactivity of Fe(iv)–oxo species with N4/N5 ligands derived from l-proline

The hydroxylation of hexane by two FeIVO complexes bearing a pentadentate ligand (N5, Pro3Py) and a tetradentate ligand (N4, Pro2PyBn) derived from l-proline was studied by DFT calculations.

A monoanionic pentadentate ligand platform for scandium-pnictogen multiple bonds

A new monoanionic pentadentate ligand is designed to accommodate Sc=E bonds (E = N, P). The imido complex is stable enough to isolate and characterize, and reacts rapidly with CO2....