Hydroxylation of simple alkanes by iodosylbenzene in catalyzed more efficiently by second tan by third generation iron(III) porphyrins

The catalytic activities of aryl-chlorinated iron tetraarylporphyrins with and without chloro substituents at the beta-pyrrole positions-third and second generation catalysts, respectively-were compared for the hydroxylation of ethylbenzene and cyclohexane by iodosylbenzene. The results reveal that despite the somewhat larger stability of the former complexes to the oxidative reaction conditions, they are less efficient catalysts than the corresponding unsubstituted complexes, which catalyze the transformation of the alkanes into their oxygenated products with almost 80% yield at more than 10% conversion. It is proposed that for the third generation catalyst the extremely shea life time of the most potent intermediate;is responsible for the relatively low efficiency in catalysis. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.