This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Pericles Stavropoulos at the University of Missouri at Rolla to develop, and mechanistically investigate, iron-based, hydrocarbon-oxidizing systems that can store oxidizing power onto a high-valent metal-oxo site, but also have the potential to delocalize oxidizing equivalents as ligand-centered radicals. To accomplish this, suitable ligands and iron reagents, which, in the presence of oxo donors, should simultaneously support a high-valent Fe(IV)=O unit and a ligand-centered p radical will be synthesized. These will be employed in the catalytic oxygenation of aliphatic and unsaturated hydrocarbons, and initial mechanistic data that indicate selective oxidation pathways will be collected. Mechanistic implications arising from the presence of both metal- and ligand-centered oxidizing equivalents, in relation to their individual roles in mediating hydrocarbon-activation processes will be determined. The proposed research work concentrates on tripodal trisamidoamine ligands, whose electron-rich character should help stabilize high-valent metal sites. These ligands possess o-phenyldiamine moieties, which, can retain one or more oxidizing equivalents following oxidative ligand rearrangement. In an effort to gain control over those stereo-electronic parameters necessary for the generation of an authentic [LoFe(IV)=O] moiety reactivity studies are will be undertaken involving [LFe(II)] and [LFe(III)] containing compounds and oxo-donor molecules to evaluate each ligand. The most suitable candidates will be tested in catalytic oxygenations of alkanes and olefins, to assess the selectivity of the process by comparison to undesirable pathways involving indiscriminate oxygenation chemistry. Metal-centered events will be examined by characterizing key intermediates generated in metal/oxo-donor interactions.
The proposed work aims at a better definition of the requirements needed to attain the elusive Fe(V)=O unit and its relation to preparing useful reagents for the selective oxygenation of hydrocarbons to commodity oxo products. Broader impacts extend beyond the training of post-doctoral, graduate, and undergraduate researchers to include involving rural K-12 students through a mobile laboratory that enables hands-on experimentation and discussion of dioxygen chemistry and producing written materials for these groups.
