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Metalloenzymes activate dioxygen to carry out a variety of biological reactions, including the biotransformation of naturally occurring molecules, oxidative metabolism of xenobiotics, and oxidative phosphorylation. The dioxygen activation at the catalytic sites of the enzymes occurs through several steps, such as the binding of O(2) at a reduced metal center, the generation of metal-superoxo and -peroxo species, and the O-O bond cleavage of metal-hydroperoxo complexes to form high-valent metal-o

Metal-dioxygen adducts are key intermediates detected in the catalytic cycles of dioxygen activation by metalloenzymes and biomimetic compounds. In this study, mononuclear cobalt(III)-peroxo complexes bearing tetraazamacrocyclic ligands, [Co(12-TMC)(O(2))](+) and [Co(13-TMC)(O(2))](+), were synthesized by reacting [Co(12-TMC)(CH(3)CN)](2+) and [Co(13-TMC)(CH(3)CN)](2+), respectively, with H(2)O(2) in the presence of triethylamine. The mononuclear cobalt(III)-peroxo intermediates were isolated an

Metal-superoxo intermediates have been invoked as reactive species in C-H bond cleavage of substrates by oxygenase enzymes. In this work, we have shown the first structurally characterized end-on chromium(III)-superoxo complex, [Cr(III)(14-TMC)(O(2))(Cl)](+), which was synthesized by reacting [Cr(II)(14-TMC)(Cl)](+) with O(2). The Cr(III)-superoxo intermediate has shown reactivities in C-H cleavage of alkylaromatics via a H-atom abstraction mechanism.

Mononuclear metal-dioxygen adducts, such as metal-superoxo and -peroxo species, are generated as key intermediates in the catalytic cycles of dioxygen activation by heme and non-heme metalloenzymes. We have shown recently that the geometric and electronic structure of the Ni-O₂ core in [Ni(<i>n</i>-TMC)(O₂)]⁺ (<i>n</i> = 12 and 14) varies depending on the ring size of the supporting TMC ligand. In this study, mononuclear Ni(II)-superoxo and Ni(III)-peroxo complex

Metal-superoxo species are believed to play key roles in oxygenation reactions by metalloenzymes. One example is cysteine dioxygenase (CDO) that catalyzes the oxidation of cysteine with O(2), and an iron(III)-superoxo species is proposed as an intermediate that effects the sulfoxidation reaction. We now report the first biomimetic example showing that a chromium(III)-superoxo complex bearing a macrocyclic TMC ligand, [Cr(III)(O(2))(TMC)(Cl)](+), is an active oxidant in oxygen atom transfer (OAT)

A Cr(V)-oxo complex bearing a macrocyclic TMC ligand, [CrV(TMC)(O)(OCH3)]2+, was synthesized, isolated, and characterized by various physicochemical methods, including UV-vis, ESI-MS, resonance Raman, EPR and X-ray analysis. The reactivity of the Cr(V)-oxo complex was investigated in C–H and O–H bond activation reactions. The reactivity of a Cr(III)-superoxo complex, [CrIII(TMC)(O2)(Cl)]+, was investigated in O–H bond activation reactions as well. By comparing reactivities of the Cr(III)-superox

A radical approach: The reaction of [Ni2(OH)2(Me2-tpa)2]2+ with H2O2 resulted in the peroxidation of a methyl group of the Me2-tpa ligand to produce a bis(μ-alkylperoxo)dinickel(II) complex (see ORTEP diagram) as a reaction intermediate for further oxidation to carboxylato and alkoxo complexes [Ni(Me1-tpa-COO)]+ and [Ni2(Me1-tpa-CH2O)2]2+. Me2-tpa=bis[(6-methyl-2-pyridyl)methyl][(2-pyridyl)methyl]amine. Supporting information for this article is available on the WWW under http://www.wiley-vch.de

A copper(II)-hydroperoxo complex, [Cu(Me(6)-tren)(OOH)](+) (2), and a copper(ii)-cumylperoxo complex, [Cu(Me(6)-tren)(OOC(CH(3))(2)Ph)](+) (3), were synthesized by reacting [Cu(Me(6)-tren)(CH(3)CN)](2+) (1) with H(2)O(2) and cumyl-OOH, respectively, in the presence of triethylamine. These intermediates, 2 and 3, were successfully characterized by various physicochemical methods such as UV-vis, ESI-MS, resonance Raman and EPR spectroscopies, leading us to propose structures of the Cu(II)-OOR spec

Mononuclear Mn(III) -peroxo and dinuclear bis(μ-oxo)Mn(III) 2 complexes that bear a common macrocyclic ligand were synthesized by controlling the concentration of the starting Mn(II) complex in the reaction of H2 O2 (i.e., a Mn(III) -peroxo complex at a low concentration (≤1 mM) and a bis(μ-oxo)Mn(III) 2 complex at a high concentration (≥30 mM)). These intermediates were successfully characterized by various physicochemical methods such as UV-visible spectroscopy, ESI-MS, resonance Raman, and X-

The reaction of [Ni2(OH)2(Me2-tpa)2]2+ (1) (Me2-tpa = bis(6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine) with H2O2 causes oxidation of a methylene group on the Me2-tpa ligand to give an N-dealkylated ligand and oxidation of a methyl group to afford a ligand-based carboxylate and an alkoxide as the final oxidation products. A series of sequential reaction intermediates produced in the oxidation pathways, a bis(mu-oxo)dinickel(III) ([Ni2(O)2(Me2-tpa)2]2+ (2)), a bis(mu-superoxo)dinickel(II) ([Ni