Redox‐State Dependent Ligand Exchange in Manganese‐Based Oxidation Catalysis

Abstract

Manganese-based oxidation catalysis plays a central role both in nature, in the oxidation of water in photosystem II (PSII) and the control of reactive oxygen species, as well as in chemical processes, in the oxidation of organic substrates and bleaching applications. The focus of this review is on efforts made to explore and elucidate the redox-dependent coordination chemistry of these manganese-based systems in solution and the mechanisms by which their catalytic redox 3432reactions proceed. We also examine the behaviour and activity of complexes that have been developed and used as models for the active sites of the corresponding enzymes, or used as catalysts in the oxidation of organic substrates. Given the current concern over the environmental and economic impact of chemical processes, manganese catalysts that use H 2 O 2 as oxidant are the primary focus of this review.

A Common Active Intermediate in the Oxidation of Alkenes, Alcohols and Alkanes with H2O2 and a Mn(II)/Pyridin‐2‐Carboxylato Catalyst

“…Hence, exchange with H 2 O and thereby incorporation of oxygen from water added together with the H 2 O 2 should be considered also. [24] Less obvious sources of oxygen are the oxygen atoms in butanedione and the acetic acid, with the latter either added to the reaction mixture or formed in situ. Each of these sources of oxygen atoms are considered in turn with 18 O labelling.…”

Effect of coordination dissymmetry on the catalytic activity of manganese catalase mimics

“…This coordination dissymmetry around the two metal ions could be essential for catalysis. However, most diMn complexes tested as MnCAT mimics have been prepared with symmetrical dinucleating ligands with a central alcoholate or phenolate group that afford synthetic models with identical environment around the two metal centers [14][15][16][17][18], while only a few ones were made from unsymmetrical ligands [19][20][21].…”

Activation of C–H, N–H, and O–H Bonds via Proton-Coupled Electron Transfer to a Mn(III) Complex of Redox-Noninnocent Octaazacyclotetradecadiene, a Catenated-Nitrogen Macrocyclic Ligand

“…Novel ligand platforms to mediate difficult redox reactions are of interest for synthetic homogeneous catalytic systems as well as biomimetic studies. Due to its prevalence in biological redox metalloenzymes, − the reactivity of Mn in various ligand platforms is a frequent subject of study. − In these systems, proton-coupled electron transfer (PCET)the coordinated (but not necessarily simultaneous) movement of electrons and protons between reactants and productsis of central interest in a number of industrially and biologically relevant reactions mediated by transition metals. − In addition to the study of biomimetic reaction chemistry at Mn, our group has a particular interest in nitrogen-rich analogues of classical ligands with the goal of generating novel, metal-containing energetic materials. − We have previously reported on the assembly of the first manganese complexes of tetrazene, the N 4 analogue of the classic redox-noninnocent α-diimine ligand (Figure ). …”