Studies of simple μ-oxo-bisiron(III)porphyrin as catalyst of cyclohexane oxidation with air in absence of cocatalysts or coreductants

Abstract

We report the use of simple μ-oxo-bis[tetraphenylporphinatoiron(III)] ([TPPFe III] 2O) as a catalyst for the selective oxidation of cyclohexane into cyclohexanone and cylcohexanol with air. This is the first time that [TPPFe III] 2O has been used as a catalyst for the aerobic liquid phase oxidation of cyclohexane in absence of any cocatalyst or coreductants. The oxidation of cyclohexane catalyzed by a very small amount of [TPPFe III] 2O gave 90% selectivity to cyclohexanol and cyclohexanone at 12.55% yield and catalyst turnover numbers of 90,000 (based on the metal) under the conditions of 398 K and 0.6 MPa. We showed that the reaction yields and the turnover numbers of the catalyst changed with reaction temperature, pressure and the amount of catalyst. In contrast with the corresponding monoironporphyrin, chloro[tetraphenylporphinatoiron(III)] (TPPFe IIICl), the oxidation of cyclohexane catalyzed by (TPPFe III) 2O with air had higher yields and greater turnovers.