CHEMICAL MODELS OF ENZYMES - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 175

inhibition of this process by CO. Results indicated that the FeMo-cofactor has a high
level of self-sufficiency and can realize of some of its functions without the protein.
Thus, a number of systems of the catalytic and noncatalytic reduction of dinitrogen to
hydrazin and ammonia and the successful synthesis of model iron- and iron-molibdenum
(vanadium) clusters have been reported. These investigations have formed a basis for
subsequent progress in mimicking the nitrogenase reaction.

6.3. Hydroxylation of organic compounds

Oxidation of organic compounds with dioxygen, for examples the conversion of alkanes
to alcohols, is highly exothermic. Nevertheless, dioxygen is a weak one-electron oxidant
and the thermodynamic barrier of the first stage of the reaction with the
formation of superoxide or is high. Involving dioxygen in a chemical reaction
requires its conversion in radical or radicaloid forms, in which they act as strong one-
electron oxidants, or into a form capable of performing two-electron oxidative processes
(hydrogen peroxide, for instance). The most traditional way for oxygen activation is its
previous reduction by a reducing agent, which is accompanied by protonation (Fig. 6.1).

The most challenging problem for chemists was mimicking the biological
hydroxylation of alkanes catalyzed by cytochrome P-450 and especially the conversion
of methane to methanol. The first principle breakthrough in this direction was the
pioneering work of Groves and his colleagues (Groves, 1997, 2000; Groves and
McGlusky, 1976; Groves Subramanian, 1984; Groves et al., 1994). The first synthetic
analog which closely mimicked the chemistry of cytochrome P450 was
(III) [Fe(III)TPP(Cl)] with iodozylbenzene as the oxidant to
effect the stereospecific epoxidation of olefins and hydroxylation of cyclohexane. This