IRON PORPHYRIN-CATALYZED HYDROXYLATION OF ETHYLBENZENE BY OZONE

The hydroxylation of ethylbenzene by ozone under catalysis of tetrames itylporphyrinato iron(III) complexes with various axial ligands was st udied in order to elucidate the principles which determine the efficie ncy of this biomimetic system. Reaction conditions were carefully chos en to ensure that oxygen-atom transfer from oxidized catalyst to hydro carbon is rate limiting. The catalyst's proximal ligand was found to a ffect both the stability and the reactivity of the high-valent iron po rphyrin intermediate l-X, the reactivity pattern being distinctively d ifferent from the related epoxidation reactions. The most pronounced a nd intriguing effect was of methanol, which stabilized the I-X complex as to completely inhibit its reactivity toward the alkane. Preliminar y results for two halogenated-porphyrin iron(III) complexes are presen ted too, to demonstrate the potential of the present system for practi cal purposes.