Cobaloximes radical transfer

Other complexes also react with propagating radicals by catalytic chain transfer.110 These include certain chromium,151 152 molybdenum152 1" and iron154 complexes. To date the complexes described appear substantially less active than the cobaloximes and are more prone to side reactions. 

It is also known that alkyl cobaloximes are subject to radical-induced decomposition.2 7 This suggests an alternative to the mechanism shown in Scheme 9.28 involving reversible chain transfer (Section 9.5). 

In abroad sense, the model developed for the cobaloxime(II)-catalyzed reactions seems to be valid also for the autoxidation of the alkyl mercaptan to disulfides in the presence of cobalt(II) phthalocyanine tetra-sodium sulfonate in reverse micelles (142). It was assumed that the rate-determining electron transfer within the catalyst-substrate-dioxygen complex leads to the formation of the final products via the RS and O - radicals. The yield of the disulfide product was higher in water-oil microemulsions prepared from a cationic surfactant than in the presence of an anionic surfactant. This difference is probably due to the stabilization of the monomeric form of the catalyst in the former environment. 

Subsequently, Cl was observed in polymerization of MMA with high concentrations of cobaloximes,77 293 phthalocyanines,14 136 294 295 and porphyrins.295 Cl is observed only when the cobaloxime was in the 2+ oxidation state and can catalyze chain transfer.296 Thus, Cl is a phenomenon that is closely connected to CCT. The first explanation involved a hydride (as in eq 31), where P is a polymer obtained from the propagating radical which has been terminated by hydrogen atom donation by Co111—H.161... 

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