Bioinspired Oxidation Catalysis with Iron Complexes

Iron-containing enzymes allow living systems to use aerial dioxygen for the selective oxidation of organic substrates. High-valent oxoiron as well as iron-superoxo and -peroxo species are the key intermediates in these biochemical transformations, but identification and characterization of these species is challenging due to their high reactivity. Synthetic iron complexes that serve as models for iron dependent metalloenzyme active sites have significantly advanced our understanding of correlations between electronic structures and reactivities of these oxidants, as well as of the enzymes’ catalytic cycles. Furthermore, bioinspired homogeneous iron catalysts promise to achieve efficient substrate conversions akin to those of the natural blueprints, foremost the selective oxygenation of C-H groups.This project aims at the amalgamation of concepts from bioinorganic and organometallic chemistry by stabilizing biorelevant ironoxo, -peroxo and -superoxo species in macrocyclic ligand scaffolds containing N-heterocyclic carbene (NHC) donors, which were previously shown to impart unique electronic structures and properties to reactive oxoiron intermediates. Based on preliminary work and in close collaborations with several partner groups within the Research Group, we plan to unravel correlations between electronic structures and reactivities for the hydrogen atom abstraction and oxygen atom transfer reactivities of a series of iron oxidants, specifically oxoiron(IV) species, ligated by tetra-NHC and NHC/N-donor hybrid macrocycles. Furthermore, we will probe the accessibility and reactivity of novel oxoiron(V) oxidants using the NHC-based ligand platforms, and we will equip the ligand scaffolds with functional groups for tuning solubilities or anchoring on solid supports. This is expected to advance this unique class of hybrid organometallic/bioinorganic iron complexes towards usable and rugged catalysts for oxidative C-H functionalization.