Cobalt manganese porphyrin

Apart from the commonly used NaOCl, urea—H2O2 has been used/ With this reaction, simple alkenes can be epoxi-dized with high enantioselectivity. The mechanism of this reaction has been examined.Radical intermediates have been suggested for this reaction, polymer-bound Mn -salen complex, in conjunction with NaOCl, has been used for asymmetric epoxidation. Chromium-salen complexes and ruthenium-salen complexes have been used for epoxidation. Manganese porphyrin complexes have also been used. Cobalt complexes give similar results. A related epoxidation reaction used an iron complex with molecular oxygen and isopropanal. Nonracemic epoxides can be prepared from racemic epoxides with salen-cobalt(II) catalysts following a modified procedure for kinetic resolution. 

Manganese porphyrins also form nitrosyl complexes. Fast (ca. 10°M s ) reaction of Mn(II) with NO yields stable MnNO complexes (73) that show a linear Mn—N—0 geometry (74). Interestingly, no reductive nitrosylation is observed for the reaction of Mn(III) with NO (73). Cobalt porphyrins also form stable nitrosyl complexes. The CoNO species obtained, for example, by reaction of NO with Co(Il) porphyrins have been explored as isoelectronic... 

Compared to polymerization with metalloporphyrins of nontransition metals, those with transition-metal complexes have not been well explored to date. Nevertheless, some metalloporphyrins of transition metals have been found to serve as initiators for controlled polymerization. Examples include manganese porphyrins for controlled ring-opening polymerization and organo-cobalt and -rhodium porphyrins for controlled addition polymerization. " -... 

Electrocatalytic oxidations (mainly epox-idation) of alkenes by manganese porphyrins [77, 78] and a Schiff-base [79] and iron and cobalt porphyrins [78] have been achieved. Hydrogen peroxide or the superoxide ion (O ) was generated electrochem-ically by reduction of dioxygen in solvents containing an acid or acid anhydride, the metal compounds as catalysts, and olefins as substrates, in the presence or absence of an axial base. The reaction was believed to take place through the formation of a high valent metal 0x0 porphyrin, produced... 

Epoxidation of olefins was catalyzed by the ruthenium(II) complex of the above perfluorinated y3-diketone in the presence of 2-methylpropanal (Scheme 50). Unfunctionalized olefins were epoxidized with a cobalt-containing porphyrin complex, and epoxidation of styrene derivatives was catalyzed by chiral salen manganese complexes (248) (Scheme 50). In the latter case, chemical yields were generally high, however, the products showed low enantiomeric excess with the exception of indene (92% ee). [Pd(C7Fi5COCHCOC7Fi5)2] efficiently catalyzed the oxidation of terminal olefins to methyl ketones with f-butylhydroperoxide as oxidant in a benzene-bromoperfluoro-octane solvent system (Scheme 50). In all these reactions, the product isolation and efficient catalyst recycle was achieved by a simple phase separation. 

Recently, the high inhibitory efficiency of metalloporphyrins has been shown in lipid peroxidation of rat brain homogenates [346]. It was found that manganese and cobalt porphyrins were very effective inhibitors of lipid peroxidation while iron and especially zinc porphyrins had very weak inhibitory activity, if any. For example, /50 values were equal to 21, 29, 212, 946 pmol 1 1 for CoTBAP, MnTBAP, FeTBAP, and ZnTBAP, respectively, where TBAP is 5,10,15,20-tetrakis [4-carboxyphenyl]porphyrin similar values were obtained for other porphyrin derivatives. 

Porphyrins, 21 14, 36, 135 -based manganese complexes, 46 400-402 as cobalt complex ligants, 44 284-290 compared to phthalocyanines, 7 75 complexes, 19 144, 145, 147 complex stability, 42 135-137 degeneracy lifting, 36 206 metalloporphyrins, DNA cleavage and, 45 271-283... 

Obirai J, Rodrigues Pereira N, Bedioui F, Nyokong T (2003) Synthesis, spectral and electrochemical properties of a new family of pyrrole substituted cobalt, iron, manganese, nickel and zinc phthalocyanine complexes. J Porphyrins Phthalocyanines 7(7) 508-520... 

The extent of metal insertion is strongly dependent on the type of metal ion. Cobalt (II), nickel (II), and zinc (II) are readily incorporated into the porphyrin ring, whereas manganese (II), iron (II), and copper (II) are difficult to insert under the same experimental conditions [335]. Self-assembled monolayers of 12 and 13 have electro-catalytic activity in the reduction of O2 to H2O and H2O2, respectively. 

In pursuit of biomimetic catalysts, metaUoporphyrins have been extensively studied in attempts to mimic the active site of cytochrome P450, which is an enzyme that catalyzes oxidation reactions in organisms. In recent decades, catalysis of alkene epoxidation with metaUoporphyrins has received considerable attention. It has been found that iron [1-3], manganese [4,5], chromium [6], and cobalt porphyrins can be used as model compounds for the active site of cytochrome P450, and oxidants such as iodosylbenzene, sodium hypochlorite [7,8], hydrogen peroxide [9], and peracetic acid [10] have been shown to work for these systems at ambient temperature and pressure. While researchers have learned a great deal about these catalysts, several practical issues limit their applicability, especially deactivation. 

Similar reactivities occur with the manganese and cobalt porphyrins to give (ClgTPP)Mnni-OO- (-AGbf, 17 kcal) and (ClgTPl>)Co> -OO (-AGbf, 8 kcal). Such... 

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