85028-59-7Relevant articles and documents
Reduction and Alkylation of Cobalt(II) Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions. A Kinetic Spectrophotometric Study
Baral, S.,Neta, P.
, p. 1502 - 1509 (2007/10/02)
The reactions of CoIITPPS (TPPS = tetrakis(4-sulfonatophenyl)porphyrin) with alkyl and hydroxyalkyl radicals have been studied by pulse radiolysis.The alkyl radicals undergo axial addition with rate constants of (1.2-1.9) * 109 M-1 s-1 to form R-CoIIITPPS complexes which either are stable (R = CH3) or undergo decomposition (R = CH(CH3)2) to CoITPPS and an olefin via a β-proton elimination mechanism (k1 = 0.3 s-1 at pH 8 and 3 s-1 at pH 13).The hydroxyalkyl radicals also form R-CoIIITPPS with rate constants of (1.1-1.2) * 109 M-1 s-1.These adducts undergo heterolytic cleavage of the cobalt-carbon bond to form CoITPPS and a carbonyl compound, with rate constants of 3.6 * 102 s-1 (R = CH2OH) and 6.2 * 103 s-1 (R = C(OH)(CH3)2).The radicals (CH3)2C.O- and C.O2- reduce CoIITPPS to CoITPPS by an outer-sphere mechanism with rate constants 7 * 108 and 2 * 108 M-1 s-1, respectively.CoITPPS is oxidized to CH3CoIIITPPS by CH3I (k2 = 3 * 105 M-1 s-1) and to CoIITPPS (probably through intermediate formation of CoIIITPPS) by N2O (k2 2 M-1 s-1).The reactivities of the present systems have been compared with those of other models suggested for vitamin B12 like cobaloximes, cobalamins, and other macrocyclic CoII complexes.
