Cobalt complexes, dioxygen activation

H-bonding interactions are useful for design of catalytic systems, imitating enz)Tnes activity. The participation of H-bonds in dioxygen binding to cobalt complexes and activation was studied in [106]. The cobalt... 

The [Con(bipy)2 ]2+ species has also been reported to activate hydrogen peroxide and ter -butyl hydroperoxide for the selective ketonization of methylenic carbons, the oxidation of alcohols and aldehydes, and the dioxygenation of aryl olefins and acetylenes (36). Later reports (37), however, while confirming that the cobalt complexes did indeed cata-... 

Although the cofacial diporphyrins represent a vibrant and innovative direction in dioxygen activation, simple porphyrins and their derivatives also remain an important research area. The dichlorophenyl-substituted porphyrin tdcpp [5,10,15,20-tetrakis(2,6-dichlorophenyl)-porphyrin] forms a complex with cobalt(II), [Co(tdcpp)], and catalyzes the oxidation of conjugated olefins to (after experimental workup) ketones in the presence of dioxygen and triethylsilane (80) a hydroperoxide intermediate has been isolated from these reactions (81). 

Collman, and co-workers (346-352) also demonstrated that pyrolitic graphite electrodes modified with cofacial bis(porphyrinato cobalt) complex (CoFTF4) can promote the four-electron reduction of O2 to H2O. According to the proposed model, the dioxygen molecule is activated by the simultaneous coordination to two cobalt porphyrin sites, but electronic factors and/or the lack of electrons can also limit the four-electron process. 

Dioxygen Activation with Sterically Hindered Tris(pyrazolyl)borate Cobalt Complexes. 

Hydroperoxo complexes can also be obtained by a one-electron reduction of the superoxo intermediates [Ru(NH3)6]2 + is one of the most convenient reducing agents for this chemistry.15 An interesting way of preparing hydroperoxides via dioxygen activation utilizes a formal 02 insertion into M-H bond in metal hydrides examples are known for platinum, rhodium, and cobalt complexes, to name just a few.14,15... 

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