Research Projects

This proposal aims to develop transition-metal catalysts featuring chelating N-heterocyclic imine (NHI) ligands for transformations such as CO₂ reduction, N₂ fixation, hydrogenation, hydrofunctionalization, dehydrogenation, and dehydrogenative coupling reactions. NHI ligands are highly valuable due to their strong electron-donating ability and stereoelectronic tunability, making them ideal for stabilizing transition-metal complexes in diverse coordination environments and oxidation states, and facilitating catalysis under mild conditions. Furthermore, the convenient synthesis of these ligands and varied methods for introducing the metal center and co-ligands offer synthetic advantages. Their ability to promote cooperative metal–ligand activation of H₂ (or hydrosilanes, hydroboranes, and organic substrates) opens new opportunities in (de)hydrogenation chemistry with transition-metals. Despite these features, the use of chelating NHI ligands in transition-metal catalysts remains largely unexplored. For example, only one example of an amido-imidazolin-2-imine type ligand is known, which was recently introduced to transition-metal chemistry. The complexes featuring this monoanionic chelate ligand were found to be effective for catalyzing H/D exchange in hydrosilanes and hydrosilylation of olefins. This underexplored potential of transition-metal complexes based on chelating NHI ligands, particularly amido-imidazolin-2-imines, for catalyzing a variety transformation is exciting. This project will synthesize a collection of new and known chelating NHI ligands, especially amido-imidazolin-2-imines, and use them to prepare transition-metal complexes, with a focus on earth-abundant first-row transition-metals. These complexes will be tested in catalytic reactions like CO₂ reduction, N₂ fixation, and hydrogenation of organic carbonates, carbamates, formates, and carboxylic acid derivatives, along with reductive amination and dehydrogenative coupling reactions. Designing efficient transition-metal-based catalysts for these reactions is crucial for practical, economic, and environmental reasons. For instance, reducing CO₂ to methanol, a versatile fuel and chemical feedstock, presents a sustainable alternative to conventional methods, addressing the urgent need to mitigate atmospheric CO₂ levels. Hydrogen for CO₂ reduction could be sourced from renewable energy-powered water electrolysis, enhancing environmental benefits. This project will also explore the mechanistic aspects of catalysis, including structure-activity relationships, Hammett and Eyring plots, isotopic labeling experiments, and DFT calculations to predict reaction pathways. In summary, this work aims to create a comprehensive library of chelating NHI ligands and transition-metal complexes, focusing on challenging, industrially relevant catalytic transformations.