Modeling Non-Heme Iron Halogenases: High-Spin Oxoiron(IV)-Halide Complexes That Halogenate C-H Bonds

The non-heme iron halogenases CytC3 and SyrB2 catalyze CT-H bond halogenation in the biosynthesis of some natural products via S = 2 oxoiron(IV)-halide intermediates. These oxidants abstract a hydrogen atom from a substrate C-H bond to generate an alkyl radical that reacts with the bound halide to form a C-X bond chemoselectively. 'The origin of this selectivity has been explored in biological systems but has not yet been investigated with synthetic models. Here we report the characterization of S = 2 [Felv(O)(TQA)(Cl/Br)](+) (TQA = tris(quinolyl-2-methyl)amine) complexes that,can preferentially halogenate cyclohexane. These are the first synthetic bxoircin(IV)-halide complexes that serve as spectroscopic and functional models for the halogenase intermediates. Interestingly; the nascent substrate radicals generated by these synthetic complexes are not as short-lived as those obtained froni heme-based oxidants and can be intercepted by 02 to prevent; alogenation, supporting an emerging notion that rapid rebound may not necessarily occur in non-heme oxoiron(IV) oxidations.