CAS: Metal-Mediated Nitrate Deoxygenation by Rationally-Designed Organic Reductants and Subsequent Nitrogen-Transfer

Indiana University, Bloomington IN

Investigators

Abstract

With this award, the Chemical Synthesis Program of the Chemistry Division of the National Science Foundation is supporting Professor Kenneth Caulton in the Department of Chemistry at Indiana University for research directed at the activation of nitrogen oxides. This project is developing new ways to incorporate nitrogen from agricultural waste into useful organic compounds. This nitrogen recycling requires chemical promoters that interact with the nitrate, rendering it reactive. The chemical promotors are chosen from among inexpensive and abundant precursors often containing silicon. The discovery strategy begins with laboratory experiments combining these silicon promotors with the nitrate. The results of these experiments are simulated mathematically, which leads to improved promotors, which are then tested experimentally. The overall process is leading to insights for the recycling of other waste products containing phosphorus, carbon, and chlorine. The project also entails a major training component; student coworkers obtain hands-on experience in both chemical synthesis and computer simulations. Professor Caulton also leads diverse outreach activities aimed toward familiarizing the public with the benefits of chemical technology. Finally, the project is preparing a group of undergraduate and graduate students with expertise in sustainability. This project targets nitrate reduction by devising new reaction methods using mechanistically-guided organic reductants and transition-metal catalysts. For the latter, redox-active ligands are being used due to their ability to promote the requires multi-electron conversions. Preliminary results reveal that nitrate reduction can be coupled to C─N bond formation. As one form of reduced nitrogen, transition metal nitrides are being combined with unsaturated organic substrates to give new concepts of reactivity, i.e., beyond electrophilicity and nucleophilicity. Value-added compounds are sought by devising methods to create new bonds between nitrosyl groups and carbon. New nitride functionalization also impacts the research areas of nitrogen fixation and N-C bond formation generally. The new synthetic methodology accomplishing efficient nitrogen transfer can potentially provide a blueprint to reduce N, P, and S containing oxyanions, providing a new entry into the field of oxygen atom transfer. Methods employ quantum calculations for predicting metal choice, species charge and substituent effects for performance optimization. This program provides effective training for coworkers in organometallic chemistry, methods development and mechanistic and computational chemistry and thus will contribute to building a highly skilled technical 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.