Oxidation of Alkanes Catalyzed by Zeolite-Encapsulated Perfluorinated Ruthenium Phthalocyanines

摘要

The oxidation of alkanes catalyzed by metal complexes is often hampered by oxidative degradation of the catalyst and/or deactivation by irreversible dimerization of the complexes. In the case of porphyrin- or phthalocyanine-based catalysts, halogenation of the macrocycle periphery has proven to be effective at enhancing the complex stability as well as the activity. The halogen substituents replace abstractable hydrogens and render the ligand less susceptible to electrophilic attack. Additionally, the central metal ion becomes easier to reduce via inductive effects. The electron-withdrawing substituents also destabilize normally unreactive μ-oxo dimers. In spite of such improvements, these systems eventually degrade. An alternative strategy to enhance the lifetime and activity of such catalysts involves site isolation of the metal complexes within the micropores of zeolites. Both porphyrins and phtha-locyanines have been encapsulated in the supercages of X- and Y-type zeolites via a variety of synthetic methods.