Determining the Inherent Selectivity for Carbon Radical Hydroxylation versus Halogenation with Fe^III(OH)(X) Complexes: Relevance to the Rebound Step in Non-heme Iron Halogenases

The first structural models of the proposed cis-Fe^III(OH)­(halide) intermediate in the non-heme iron halogenases were synthesized and examined for their inherent reactivity with tertiary carbon radicals. Selective hydroxylation occurs for these cis-Fe^III(OH)­(X) (X = Cl, Br) complexes in a radical rebound-like process. In contrast, a cis-Fe^III(Cl)₂ complex reacts with carbon radicals to give halogenation. These results are discussed in terms of the inherent reactivity of the analogous rebound intermediate in both enzymes and related catalysts.