Exploring Hydrogen-Atom- and Hydride-Transfer Non-Innocent Ligands

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In this project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division of NSF, Professor Alan F. Heyduk of the Department of Chemistry at the University of California, Irvine is developing a new class of ligand for use in the development of catalytic reactions. The principal goal of this research program is to understand the fundamental ligand properties that enable hydrogen-atom and hydride transfer reactivity so new coordination complexes can be designed to serve as catalysts in reduction reactions of importance in fine and commodity chemical synthesis and in the recycling of abundant chemical feedstocks such as carbon monoxide and carbon dioxide. The fundamental nature of the project, which lies at the interface of organic, organometallic and inorganic chemistry, is broadly appealing to chemists at all education levels and is particularly well-suited to advanced levels of chemical education. Towards this end, the project includes a strong component that encourages underrepresented groups to pursue advanced degrees in STEM research areas. Redox-active or redox non-innocent ligand platforms are well established in inorganic and organometallic chemistry for their ability to engender adventitious electronic properties in simple coordination complexes. Such properties have been exploited in catalysts for multi-electron reactivity, in photosensitizers for charge-transfer applications, and in the synthesis of materials with advanced electrical and magnetic properties. The work proposed herein will develop a new type of ligand non-innocence that leverages both electron- and proton-transfer abilities of catecholate-type ligands to achieve ligand-centered hydrogen-atom transfer (HAT) and hydride transfer (HT) reactivity. In this project, two related pincer-type ligands will be examined to answer several fundamental question of broad applicability: (a) What are the thermodynamic limits of ligand-based HAT and HT reactivity? (b) What is (are) the molecular-level mechanism(s) of ligand-based HAT and HT reactivity? (c) Can ligand architecture and metal ion selection be used to tailor this ligand-based reactivity to favor selectively HAT or HT reactivity through the manipulation of thermodynamic or kinetic factors?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.