Biomimetical catalytic activity of iron(III) porphyrins encapsulated in the zeolite X

• Published in: Journal of molecular catalysis. A, Chemical Vol. 160; no. 2; pp. 199 - 208
• Main Authors: Rosa, I.L.Viana, Manso, C.M.C.P, Serra, O.A, Iamamoto, Y
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.10.2000; Elsevier
• Subjects: Biomimetic catalyst; Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Hydrocarbon oxidation; Ironporphyrin; Ironporphyrin encapsulation; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites; Ironporphyrin encapsulation; Ironporphyrin; Hydrocarbon oxidation; Biomimetic catalyst; Zeolites; Catalytic reaction; Hydrocarbon; Hydroxylation; Nitrogen heterocycle; Biomimetic reaction; Organic ligand; Selectivity; Zeolite; Molecular sieve; Macrocycle; Intercalation compound; Heterogeneous catalysis; Hydrogen abstraction; Iron III Complexes; Alkane; Cyclohexane; Epoxidation; Oxidation; Metalloporphyrin; Catalyst; Ethylenic compound; Modified material
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(00)00214-4

The approach adopted for the obtention of zeolite-encapsulated FeP led to clean syntheses of biomimetical catalyst. The catalysts were obtained through the zeolite synthesis method, where NaX zeolite was synthesised around one of the cationic FePs: iron(III) 5,10,15,20-tetrakis(4- N-methylpyridyl)porphyrin (FeP 1) or iron(III) 5-mono(2,6-dichloro-phenyl)10,15,20-tris(4- N-methylpyridyl)porphyrin (FeP 2). The syntheses yielded pure FeP 1NaX and FeP 2NaX catalysts without any by-products blocking the zeolite nanopores. FeP 1NaX and FeP 2NaX efficiently catalysed the epoxidation of ( Z)-cyclooctene by iodosylbenzene (PhIO) in DCE, giving rise to cis-epoxycyclooctane yields of 85% and 95%, respectively. Hydroxylation of adamantane shows a preferable alkane oxidation at the tertiary CH bond, indicating a hydrogen abstraction through the Fe IV(O)P ·+species in the initial step. The total adamantanol yields were 52% and 45% for FeP 1NaX and FeP 2NaX, respectively. Concerning selectivity, FeP 1NaX and FeP 2NaX gave an 1-adamantanol (Ad-1-ol)/2-adamantanol (Ad-2-ol) ratio of 20:1 and 11:1, respectively (after statistical correction). Therefore, these results indicate a free radical activation of the CH bonds of adamantane as expected for P-450 models. In the cyclohexane oxidation catalysed by FeP 1NaX in DCE, a cyclohexanol (C 6-ol) yield of 50% and an alcohol/ketone ratio of 10 was obtained. The hydroxylation occurs according to the so-called oxygen rebound mechanism, as expected for a P-450 model system. FeP 2NaX is less selective (C 6-ol yield=25% and alcohol/ketone=1.2). One possible explanation is that a Russell-type mechanism involving O 2 imprisoned within the zeolite cages may be operating parallelly, generating both C 6-ol and cyclohexanone.