Metalperoxo

Metalperoxo refers to coordination complexes in which a peroxide fragment (O2^2−) is bound to a metal center. These species are key intermediates in dioxygen activation and are studied across transition metals, including iron, copper, manganese, cobalt, ruthenium, and others. They can adopt several structural motifs: terminal metal–peroxo (M–OO), side-on η2-O2 coordinated to a single metal, and μ-oxo-bridged or μ-η2:η2 dinuclear arrangements where the O2 unit is shared between two metals. Some related species are hydroperoxo (HO2−) ligands, formed by protonation of peroxo or by different reaction pathways.

Formation and reactivity: Metalperoxo complexes form by binding O2 to reduced metal centers, or by reacting metal-oxo or metal-hydroxide species with hydrogen peroxide or O2. They are involved as reactive intermediates in enzymatic and synthetic oxidation chemistry. Reactions include O–O bond cleavage to generate metal-oxo species, O-atom transfer to substrates, and various oxidation of hydrocarbons, sulfides, and organic molecules.

Spectroscopy and detection: They are characterized by UV–visible spectroscopy and resonance Raman, with O–O stretching vibrations typically appearing in the range of about 800–900 cm−1 for intact peroxo ligands; shifts reflect binding mode and metal identity.

Applications and significance: Metalperoxo complexes illuminate mechanisms of oxygen activation by metals and inform the design of oxidation catalysts and biomimetic systems. They bridge fundamental inorganic chemistry with practical catalysis and biochemistry.