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

This project is funded by the Chemical Synthesis program of the Chemistry Division. Professor Lawrence Que of the University of Minnesota prepares iron compounds that mimic biological molecules that convert normally unreactive species to more useful ones. An example is the conversion of methane, the main component in natural gas, to methyl alcohol, an industrially important feedstock. Since the biological systems have only fleeting existence, they are very difficult to study. The model compounds prepared in this project are designed to be more stable than the biological ones. The additional stability permits an investigation of exactly how the biological systems function. This not only reveals basic biochemical information, but also allows the design of 'bio-inspired' catalysts for difficult reactions with industrial and environmental applications. Additionally, the project educates graduate students in a multidisciplinary context. The training and development that these students receive is critically important for preparing the next generation of domestic science and technology personnel capable of competing in the global marketplace.

The primary goal of the research is to generate synthetic analogs of the mononuclear nonheme iron enzymes that activate oxygen. Toward this goal complexes of doublet spin Fe(IV)=O and Fe(V)=O are prepared and characterized by X-ray crystallography and spectroscopic methods including EPR, Mössbauer, resonance Raman, NMR, and X-ray absorption. These methods provide a detailed insight into the geometric and electronic structures of the complex. This information is used to understand the electronic factors that govern the reactivity of a high-valent iron-oxo center. The results guide the development of catalysts for the oxidations of C-H bonds. This project provides training for graduate students and requires them to gain expertise in synthesis, design, spectroscopy, kinetics and mechanism, and to interpret these results in light of related biochemical and computational studies.