Reactive oxygen species , chromium

Already in 1982, it was suggested that the intermediate chromium(V) state is involved in the carcinogenic process.9 Reactive Cr(V) and Cr(IV) intermediates may be harmful in many ways acting as tyrosine phosphatase inhibitors, or by forming organic radicals upon reaction with cellular reductants, which in turn can react with O2 and lead to reactive oxygen species.10 Reaction of chromium(VI) with... 

Tsou TC, Yang JL. 1996. Formation of reactive oxygen species and DNA strand breakage during interaction of chromium(IU) and hydrogen peroxide in vitro Evidence for a chromium(III)-mediated Fenton-like reaction. Chem Biol Interact 102 133-153. 

The mechanism of oxygen transfer from the peroxide (29) to the substrate still remains a matter of controversy. Current opinions favor the formation of a high-valent FeO (or Fe =0 or Fe —0-) (30) active species, which acts as a homolytic hydrogen abstractor from the substrate. An alternative mechanism considers the Fe -peroxide complex as the actual hydroxylating reagent, by analogy with the reactivity of vanadium(V)-peroxo and -alkylperoxo complexes and that of chromium(Vl)-peroxo complexes (see below). ... 

Chromium-carbene complexes can be prepared from 2- and 3-substituted indolyllithium compounds and chromium hexacarbonyl, followed by methylation. These reactive species combine with alkynes to give cyclization products, which are oxygenated carbazoles. Oxidation to the quinone can be effected with ceric ammonium nitrate (can) where possible, otherwise the product is a cyclohexadiene (Scheme 66) <89JOC3249>. 

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