Main Group Catalysts for Activation Chemistries

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With this award, the Chemical Catalysis Program of the NSF Division of Chemistry is supporting the research of Professor Alexander Radosevich of the Massachusetts Institute of Technology who is studying a new class of catalysts based on lightweight, inexpensive, and abundant nonmetal elements. Catalysis plays a central role in the scalable, economical, and sustainable synthesis of chemicals, including fuels, drugs, and materials. The development of new catalysts based on inexpensive and earth-abundant elements underpins emerging reaction chemistries and advances society's goals for sustainability. In this project, Dr. Radosevich and his students are creating new phosphorus-containing compounds that react with simple and naturally occurring compounds such as alcohols and ammonia. The specific reactions being pursued in this research include schemes to remove oxygen from alcohols and electrochemically oxidize ammonia, both of which may contribute to the renewable production of chemicals and the conversion of energy, respectively. Graduate and undergraduate researchers working with Dr. Radosevich are receiving training in a broad set of spectroscopic, physical, and synthetic chemistry techniques. Achieving these training objectives contributes to a vital workforce that underpins the economic competitiveness of US chemistry-based industries. Dr. Radosevich and his research group participate in a number of outreach efforts advancing the goal of broad participation in science. Dr. Radosevich's laboratory is also host to numerous visiting international researchers at all levels of experience, contributing to ongoing US leadership in international scientific engagement.Dr. Radosevich is pursuing the experimental physical, thermodynamic, and mechanistic foundations for the development of a broad new class of redox active nonmetal catalysts based on phosphorus. This work centers on the proposition that enforcing nontrigonal geometries on tricoordinate phosphorus compounds will yield the structural and electronic conditions necessary to support catalytic reactivity initiated by O-H and N-H activation. The experiments establish new main group-based approaches to alcohol deoxygenation and ammonia oxidation at nontrigonal tricoordinate phosphorus. Specific areas being addressed include delineating the role and magnitude of substituent effects on the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) electronic structure of nontrigonal tricoordinate phosphorus compounds and establishing trends in experimental bond enthalpies for pentacoordinate alkoxyphosphoranes through bond cleavage to open-shell tetracoordinate phosphoniumyls. The research also develops elementary reaction chemistry at nontrigonal tricoordinate phosphorus catalysts supporting a new N-N bond forming reaction pursuant to N-H activation. Together, these studies are providing a detailed, experimental quantification of the impact of nontrigonal distortion on electronic structure in tricoordinate phosphorus that are enabling p-block redox catalysis for a range of small molecule conversion reactions. Apart from the scientific objectives, this project supports the technical training and development of undergraduate and graduate students, facilitating the maintenance of a well-trained domestic chemical workforce.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.