Biomimetic nonheme iron catalysts for alkane hydroxylation

The catalytic functionalization of alkanes under mild conditions is a subje ct of great current interest. Nature has evolved a number of metalloenzymes such as the heme-containing cytochrome P450 and the nonheme methane monoox ygenase, which are capable of effecting such transformations. There has thu s been significant interest in modeling such enzyme active sites and develo ping biomimetic alkane hydroxylation catalysts. In this review, the efforts of the last 10 years in the development of nonheme iron catalysts are summ arized and discussed. These catalysts typically act in concert with ROOH or H2O2. With ROOH as oxidant, it is clear from mechanistic studies that alko xyl radicals are the principal agents that cleave the alkane C-H bond to ge nerate long-lived alkyl radicals. This conclusion, for the most part, appli es also for oxidations involving H2O2. In a few cases, however, stereospeci fic alkane hydroxylation is observed. For these instances, there is evidenc e from (H2O)-O-18 exchange experiments that a high-valent iron-ore species is involved. (C) 2000 Elsevier Science S.A. All rights reserved.