RUI: Large Kinetic Isotope Effects as Mechanistic Indicators in Organometallic Chemistry

With support from the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Miriam A. Bowring of the Department of Chemistry at Reed College is working with undergraduate researchers to study the fundamental mechanisms of chemical reactions with potential applications to greener alternative fuels. One main tool for finding out how reactions work is the study of reaction rates. It has been observed that some reactions involving hydrogen are much faster than expected compared to the corresponding reactions with deuterium. The researchers aim to determine the mechanisms that cause such unusual observation, which could lead to improved understanding of chemical reactivity. Furthermore, the group is collaborating with high school chemistry teachers on research in reclaiming palladium in road dirt as a catalyst, which may attract broader student interests in STEM (science, technology, engineering and mathematics). Anomalously large kinetic isotope effects (KIEs) are occasionally observed during mechanistic investigations of promising organometallic catalysts. The mechanistic origins of large KIEs are not well understood, and are often ascribed to proton tunneling. The proposed research encompasses mechanistic study of two systems with large observed KIEs: protonolysis to release methane from platinum methyl complexes, and formic acid dehydrogenation with an iridium-ruthenium bimetallic catalyst. To determine the origins of the large KIEs in these systems, kinetic studies will be performed while systematically adjusting variables such as reaction concentration, stoichiometry, and temperature, properties of the organometallic fragments, and the acid. 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.