Selective low temperature hydroxylation of isobutane by molecular oxygen catalyzed by an iron perhaloporphyrin complex

Irontetrakis(pentafluorophenyl)β-octabromoporphyrinato complexes have been synthesized for the first time and shown to have unprecedented catalytic activity for the reaction of molecular oxygen with isobutane to givetert-butyl alcohol. This is the first report of the use of a perhaloporphyrin complex for mild, selective air-oxidation of an alkane and extends the trend of increased activity with halogen substitution established previously. Replacing the eight β-(pyrrolic) hydrogens in Fe(TPPF20) complexes with bromines gives catalysts having twice the room temperature air-oxidation activity of the Fe(TPPF20) complexes. Room temperature reaction of isobutane with oxygen catalyzed by Fe(TPPF20β6-Br8)Cl produces 190 moles product per mole catalyst per hour with over 90% selectivity to the alcohol. The catalyst activity is unchanged after 74 hours.