Comparative study of hydrocarbon oxygenation with ironchlorins and ironporphyrins as catalysts in homogeneous and heterogeneizated systems / Estudo comparativo da oxigenação de hidrocarbonetos com ferroclorinas e ferroporfirinas como catalisadores em meio homogêneo e heterogeneizados

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In this work, the cyclohexane oxidation and the (Z)-cyclooctene epoxidation with iodosylbenzene (PhIO) e H2O2 as oxidants were studied. A comparison between fluorinated FeIIIchlorins and FeIIIporphyrins, [Fe(TFPCMG)]Cl, [Fe(TFPCMGCH3)]Cl2, [Fe(TFPP)]Cl, [Fe(TF4TMAPP)](CF3SO3)5 as catalysts was made either in solution or supported in silica matrices via eletrostatic interaction and/or covalent bonds. In the case of (Z)-cyclooctene epoxidation by PhIO, all the studied metallocomplexes achieved high yields for the epoxide production in both homogeneous and heterogeneous systems. The catalytic activity was maintained even after three successive recyclings. On the other hand, when H2O2 was used as oxidant the yields were lower. Differently, raised yields of epoxidation were observed when using methanol as solvent due to favored formation of the active intermediate FeIIIhydroperoxide. The performance of the heterogeneous systems was significantly lower than that of the catalysts in solution. The best yields were observed with DCE, a viscous solvent that probably raises the shelf life of the solvent cage favoring the biomimetic process. The supported systems were characterized by EPR and UV-Vis spectroscopies. These techniques gave information about the oxidation state and the metal spin, as well as the macrocycle geometry on the solid matrix surface. The catalytic results were explained by the nature of the functional groups that bound the metallocomplex to the silica matrix. In addition, the information obtained by the EPR technique regarding the state of oxidation of iron and the geometry of the supported metallocomplexes gave consistence to the proposed mechanisms in the oxidation processes.

ASSUNTO(S)

fe(iii)chlorin fe(iii)porphyrin ferroclorinas e ferroporfirinas catalisadores hidrocarbonetos catalyst oxidation

ACESSO AO ARTIGO

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