Halogen substituent effects on the catalytic activity of iron porphyrin complexes for selective air-oxidation of alkanes in the liquid phase

Abstract

Halogenation of the porphyrin ring of porphyrinatoiron(III) complexes greatly increases their catalytic activity for the selective mild reaction of alkanes with molecular oxygen. The greater the halogen content the greater is the catalytic activity of the complex. Selective reaction of isobutane and propane with molecular oxygen is catalyzed bytetrakis(pentafluorophenyl)porphyrinatoiron(III) azido, hydroxo, or halo complexes under mild conditions of temperature and pressure. No added co-reductant is required in these systems. Catalytic oxidation of isobutane in the presence oftetrakis (pentafluorophenyl)porphyrinatoiron(III) hydroxide at room temperature gavetert-butyl alcohol in 95% selectivity. The catalyst activity was virtually unchanged after over 140 hours at room temperature and over 12,000 turnovers (moles of alcohol produced/mole of metal complex used) of isobutane to the alcohol were observed.