Asymmetric cationic methyl pyridyl and pentafluorophenyl porphyrin encapsulated in zeolites: A cytochrome P-450 model

Abstract

In this work the iron(III)tris(4- N-methylpyridyl)-mono(pentafluorophenyl)-porphyrin, [Fe{T(4- N-MePy)MFPP}]Cl 4, was impregnated (FeP-NaY imp) and encapsulated (FeP-NaY) in the NaY zeolite and had been used as catalyst in the hydrocarbon oxidation by iodosylbenzene (PhIO) in 1,2-dichloroethane. Cyclohexane, ( Z)-cyclooctene and adamantane were used as substrate. In the case of cyclohexane, both homogeneous (FePCl 4) and heterogeneous (FeP-NaY imp and FeP-NaY) systems are 100% selective towards the formation of cyclohexanol, indicating that oxygen rebound mechanism is operating. The same systems were able to epoxide ( Z)-cyclooctene with yields of 92% of cis-epoxycyclooctane for heterogeneous catalysts. For the FePCl 4 system the yield of cis-epoxycyclooctane obtained was 40%. Probably, this fact is due the low solubility of the FeP in this organic media (1,2-dichloroethane) because when the Cl − counter-ions were exchanged for PF 6 − and the solvent used was a mixture consisting of 1,2-dichloroethane/acetonitrile (1:1) the yield of cis-epoxycyclooctane increased from 40 to 95%. Hydroxylation of adamantane shows a preferable alkane oxidation at the terciary C H bonding as expected for a P-450 model system. The total adamantanol yields were 58, 66 and 81% for [Fe{T(4- N-MePy)MFPP}]Cl 4 in solution, [Fe{T(4- N-MePy)MFPP}]Cl 4-NaY imp and [Fe{T(4- N-MePy)MFPP}]Cl 4-NaY, respectively. Concerning selectivity, the 1-adamantanol (Ad-1-ol)/2-adamantanol (Ad-2-ol) ratio of 19:1 for [Fe{T(4- N-MePy)MFPP}]Cl 4 in solution, 19:1 for [Fe{T(4- N-MePy)MFPP}]Cl 4-NaY imp and 17:1 for [Fe{T(4- N-MePy)MFPP}]Cl 4-NaY were obtained (after statistic correction). These data indicate a free radical activation of the C H bonds of adamantane, as is expected for a P-450 model. 2-Adamantanone was not obtained in any of the cases.