Manganese-dioxygen complexes

Ketones are resistant to oxidation by dioxygen in aqueous solutions at T= 300-350 K. Transition metal ions and complexes catalyze their oxidation under mild conditions. The detailed kinetic study of butanone-2 oxidation catalyzed by ferric, cupric, and manganese complexes proved the important role of ketone enolization and one-electron transfer reactions with metal ions in the catalytic oxidation of ketones [190-194],... 

Although these cobalt species do not in themselves activate dioxygen, they do exhibit similarities to the proposed structures of manganese complexes that may be involved in photosynthetic water oxidation... 

Proserpio, D.M., Rappe, A. K., and Gorun, S.M. (1993) Theoretical modeling of the mechanism of dioxygen activation and evolution by tetranuclear manganese complexes, Inorg. Chim. Acta 213, 319-24. 

Abu-Omar MM (2011) High-valent iron and manganese complexes of corrole and porphyrin in atom transfer and dioxygen evolving catalysis. Dalton Trans 40 3435-3444... 

The catalase-like function of the manganese complex was evaluated by measuring the volume of dioxygen collected in a gas burette, which evolved from the solution (total volume 4ml) containing the manganese complex (50mg) and hydrogen peroxide (1ml, 30%) in different solvents (water, dimethylformamide and methanol) at 0°C and 25 C. 

Catalytic oxidations using manganese complexes and dioxygen or peroxide oxidants are rather rare. Although reversible dioxygen adducts of the superoxo or peroxo type have been detected in the interaction of manganese(II)-pophyrin or -Schiff base complexes with O2 at low tem-... 

His research interests include catalysis by cobalt, iron and manganese, complexes (biomimetic dioxygen activation, catalytic oxidation and carbonylation), as well as kinetics and mechanisms of inorganic reactions in solution (fast redox and electron transfer). 

The complex can be viewed as a dimer of MnnMnm dimers joined by a single oxygen bridge, with the four manganese atoms assuming a chain disposition. It is interesting to note the presence of two coordinated water molecules (01), even if their positions at opposite ends prevent any possible mutual interaction to form an 0-0 bond able to lead to the development of dioxygen. 

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