RUI: primary and secondary coordination sphere effects in ruthenium-catalyzed base-free hydrogen transfer reactions

This three-year, $219,632 Project Grant from the National Science Foundation's Division of Chemistry and Mathematical and Physical Sciences program will support the development of new base-free ruthenium-catalyzed hydrogen transfer reactions. Principal Investigator Steven Kalman of Stockton University is working to design catalysts that can add hydrogen to organic compounds under milder conditions without the need for specialized equipment or hydrogen gas storage. The goal is to simplify and reduce the cost of important hydrogenation reactions used in pharmaceutical, fragrance, and fine chemical synthesis. Dr. Kalman and his students are studying how ligand structure impacts the catalytic activity of ruthenium complexes to create more active and selective catalysts for hydrogenation and acceptorless dehydrogenation reactions. In addition to organic synthesis applications, these reactions also have potential relevance for hydrogen storage. The grant also supports research training for undergraduate students from diverse backgrounds, preparing them for STEM careers.

Abstract

With support from the chemical catalysis program in the division of chemistry, steven kalman of stockton university is studying the development of new catalysts that can add hydrogen to organic compounds (hydrogenation). These reactions are important for making products ranging from pharmaceuticals to fragrances and any number of fine chemicals. Traditionally these types of reactions are done using specialized equipment and hydrogen gas. The work proposed here bypasses the storage of hydrogen by generating hydrogen during the reaction from readily available precursors. Another emphasis of this research is to make the reactions simpler and less expensive. This will be done through design by constructing catalysts that perform hydrogenations using mild conditions. This funding will support the work of undergraduate students from diverse backgrounds by providing training in various chemistry techniques and an immersive summer research experience. This unique opportunity is preparing them for both obtaining advanced degrees in science fields and contributing to a globally competitive stem (science, technology, engineering and mathematics) workforce. The hydrogenation of double and triple bonds is an important reaction in the synthesis of various organic compounds. Transfer hydrogenation is a reaction that uses an easily handled reagent like isopropyl alcohol as a substitute for hydrogen gas, negating the use of specialized equipment associated with using gaseous reagents. Most catalysts for this reaction require the use of base additives and/or an atmosphere free of oxygen and moisture. DR. Kalman and his research group are developing new ruthenium catalysts based on imidazole carboxamide ligands that operate under aerobic conditions and without additives, which allows for a simpler and less expensive reaction setup. These catalysts operate by metal-ligand cooperation in which the ligand participates in the bond breaking and bond forming steps rather than acting solely as a spectator in the reaction. Specifically, DR. Kalman and his students are studying how modifications to the ligand structure impact the catalytic activities of the ruthenium complexes, leading to the development of more active and selective catalysts. Further, they are applying these new catalysts to other organic reactions such as acceptorless dehydrogenation, a reaction that is important in both organic synthesis and hydrogen storage. 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.