Heterobimetallic Group 9 Complexes for C-F Bond Activation

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With this award, the Chemical Synthesis Program of the Division of Chemistry is supporting Professor Connie Lu of the University of Minnesota–Twin Cities, Department of Chemistry, to study organofluorine compounds; that is, chemical compounds that feature a carbon fluorine (C-F) bond. Organofluorine compounds are used as medicinal agents, insecticides, refrigerants, fire-fighting foam and stain-protective coatings for furniture and carpet. The C−F bond is especially strong and resistant to cleavage. As a consequence, organofluorines can persist and accumulate in the environment and physiologically. This project seeks ways to chemically degrade organofluorines by breaking the relatively unreactive C-F bonds and replacing all the F atoms with H atoms. The methods are to utilize rhodium and iridium catalysts to insert into the C-F bond, with molecular hydrogen serving as the reductant and H source. The project contains a strong educational component in which undergraduate and graduate students are trained for future careers in science and technology. For outreach, Dr. Lu will partner with science teachers at Antwatin Middle School with a majority of underrepresented students (50% African American, 26% Hispanic) to develop hands-on experiments related to energy and sustainability.Heterobimetallic Group 9 (Rh or Ir) complexes where the transition-metal has a formally zero or subvalent oxidation state and is braced are being investigated as reagents and catalysts for heat- or light-activated hydrodefluorination reactions. The metal centers in these Rh/Ir complexes are braced by sigma acceptor metalloligands and provide for electron rich character and engender enhanced nucleophilicity upon these metal centers thereby promoting C-F bond activation. The specific objectives of this project are to: (1) to synthesize and characterize heterobimetallic group 9 complexes bearing formal M(0) and M(-1) centers; (2) to investigate stoichiometric heat- and light-driven C-F bond activation facilitated by the heterobimetallic complexes; and, ultimately, and (3) to develop catalytic reactions that feature C-F bond activation as a key step. If successful, an important long term broader scientific impact of this research will reside in the development of fundamentally new chemistry to address the societal need to degrade pervasive perfluoroalkyl compounds.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.