Redox-Active Carborane Clusters for Metal-Free Bond Activation

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With funding from the Chemical Synthesis program in the Chemistry Division, Dmitry Peryshkov from the Department of Chemistry at the University of South Carolina at Columbia, will investigate redox-active carborane clusters for metal-free bond activation. The industrial preparation of many pharmaceuticals, plastics, dyes and electronic materials involves the precise breaking and forming of chemical bonds. Performing these bond activations is challenging and a diverse range of catalysts have been developed to perform them. Many of these catalysts require compounds of scarce, precious metals such as palladium, rhodium, iridium, and gold. However, their use is becoming increasingly problematic due to concerns around cost, abundance, and sustainability. Relevant to this challenge, this project is directed toward developing reactive bond-breaking and forming systems that do not contain metals. The project is focused on metal-free systems featuring carborane clusters, which are compounds of less toxic, earth-abundant, and inexpensive elements – boron, carbon, phosphorus, and hydrogen. The project is directed toward expanding fundamental knowledge of main group element chemistry and reactivity patterns involved in sustainable chemical transformations. The project involves increased participation of pre-college and undergraduate students in research and chemistry, especially those from demographics typically underrepresented in science, technology, engineering, and mathematics (STEM) fields, including from Historically Black Colleges and Universities, such as Claflin University, the oldest HBCU in South Carolina.The main focus of this project is the synthesis of metal-free carborane frameworks that have the ability to donate and accept electrons through donor sites and to cycle through two-electron redox states. The chemical properties of these redox-active carboranyl clusters are utilized to enable bond activation reactions. The ability of the bis(phosphino)-closo-carborane cage to accept two electrons and become a dianionic open nido-cluster while breaking a bond in a substrate and the two phosphines converting to phosphonium cations will be studied. The overall reactivity may be described as the oxidative addition of a substrate to the whole carboranyl diphosphine molecule. This work will endeavor to establish the design principles for enhancing reactivity based on electrochemical data, structural and spectroscopical parameters, and computation. In order to establish the thermodynamic and kinetic parameters for bond activation reactions promoted by these cluster compounds, studies of the transfer of electrons and protons in the metal-free reduction of unsaturated carbonyl compounds will be conducted.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.