High-Valent Nonheme Iron-Oxo Complexes: Synthesis and Reactivity

This research award from the Chemical Synthesis (SYN) program supports work by Professor Lawrence Que of the University of Minnesota to study iron facilitated oxidation processes that are important in biology and in industrial settings. Gaining insights into how Nature carries out the oxidation of strong C-H bonds efficiently plays an important role in the design of oxidation catalysts for large scale chemistry that will be more energy efficient, more environmentally friendly, and less wasteful of our resources. Professor Que is working closely with many graduate students and postdoctoral associates from diverse backgrounds and preparing them to become the leaders among the next generation of chemists.

The proposed research aims to generate synthetic analogs of high-spin (S = 2) iron(IV)-oxo intermediates that serve as the key oxidants for many nonheme iron oxygenases. The vast majority of synthetic oxoiron(IV) complexes described to date have intermediate spin (S = 1), which DFT calculations predict to be much less reactive than their high-spin counterparts. To test the DFT prediction, we will synthesize complexes with high-spin Fe(IV)=O units and characterize them by X-ray crystallography whenever possible and by a combination of spectroscopic methods in order to gain detailed insight into their geometric and electronic structures. The abilities of the high-spin complexes to oxidize substrate C-H bonds will be correlated with their properties and compared to those of low-spin Fe=O complexes to determine what factors control Fe=O reactivity. A greater understanding of such factors will be important for the development of more effective C-H bond oxidation catalysts.