Stereocontrolled and Aerobic Oxidative Reactions at High-Valent Nickel Centers

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With funding from the Synthesis Program of the Chemistry Division, Dr. Liviu Mirica of the Department of Chemistry at Washington University in St. Louis is investigating the role of nickel compounds in important chemical transformations. These include reactions that couple two different molecular partners ("cross-coupling") with improved selectivity, as well as reactions related to the activation of inert organic substrates with oxygen. Cross-coupling reactions sped up by metal-containing compounds have become indispensable in the synthesis of a large number of important chemicals, pharmaceuticals, and materials. While palladium-based catalysts are the most commonly used, Dr. Mirica is synthesizing and studying nickel (Ni)-based catalysts as they may be able to react with a wider variety of target molecules and with more specificity. In addition, Professor Mirica has established a collaboration with Professor Tim Hubin from Southwestern Oklahoma State University (SWOSU), a regional university in Oklahoma that has an appreciable amount of students that belong to underrepresented groups. Professor Hubin and his students collaborate on the synthesis of some of the targeted catalysts, visiting the Mirica lab, and performing reactivity studies using their chemical systems. This experience exposes the undergraduate students to an R1 research institution, and inspires them to pursue advanced degrees in chemistry. Professor Mirica and his group continue to work closely with collaborators from Spain and South Korea. This collaborative experience is an excellent training ground to prepare them to work in a true international environment, very similar to a multinational corporation.While palladium (Pd)-based catalysts are arguably the most commonly used in cross-coupling reactions, Ni-based cross-coupling catalysts have been developed recently. Given their ability to engage alkyl electrophiles and nucleophiles in stereospecific or stereoselective transformations the Ni-based catalysts are of interest. By comparison to the Pd-mediated transformations that generally employ diamagnetic intermediates, the Ni systems can more easily undergo one-electron redox reactions and lead to additional reaction pathways. The presence of paramagnetic Ni(I) and Ni(III) species makes reactivity characterization more difficult. Dr. Mirica's laboratory is synthesizing isolated organometallic Ni(III) and Ni(IV) complexes supported by flexible multidentate ligands and studying in detail their involvement in important chemical transformations such as stereocontrolled C-C bond formation reactions and aerobic oxidative reactions mediated by high-valent Ni intermediates. This work has direct relevance to C-H functionalization and C-C / C-heteroatom bond formation reactions. Dr. Mirica is also recruiting graduate and undergraduate students from different backgrounds and providing them with an interdisciplinary training that spans inorganic, organic, and physical chemistry.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.