(beta-octafluoro-meso-tetraarylporphyrin)manganese complexes: Synthesis, characterization and catalytic behaviour in monooxygenation reactions

The synthesis and characterization of manganese complexes of beta-octafluor o-meso-tetraarylporphyrins are reported. The presence of the electron-withd rawing beta-fluorine atoms induces a very large shift of the redox potentia l for the oxidation of the manganese(II) derivatives. With the meso-aryl gr oup bearing two ortho-chlorine atoms (2,6-dichlorophenyl) or five fluorine atoms (pentafluorophenyl), metal complexation leads to the isolation of pur e manganese(II) compounds. The stability and catalytic activity of these ne w derivatives have been studied using hydrogen peroxide and iodosylbenzene as oxidants, and standard substrates for epoxidation and hydroxylation reac tions. The results are compared to those obtained with the beta-hydrogenate d analogs under the same conditions. In the case of hydrogen peroxide, the high level of porphyrin degradation prevents efficient catalytic activity. With iodosylbenzene as oxidant, both stability and epoxidation are similar to those of the beta-hydrogenated porphyrins, however, a substantial improv ement in the efficiency of the hydroxylation of cyclohexane is observed wit h up to 33 turnovers with (perfluorotetraphenylporphyrin)manganese(II).