CAREER: Synthesis and characterization of manganese complexes toward earth-abundant green catalysts

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Chemical reactions are often inefficient, that is, they require considerable energy, or produce undesirable byproducts. Many industrial and laboratory reactions utilize catalysts - substances that lower the energy required for a reaction and/or guide the course of the reaction to specific products. As many current catalysts require the incorporation of expensive and/or toxic metals, the development of new catalysts based on inexpensive, abundant, and non-toxic replacements is an important goal. To this end, Professor David Lacy in the Chemistry Department at the University at Buffalo is supported by the Chemical Synthesis Program of the Chemistry Division to synthesize and characterize new manganese catalysts. Manganese (Mn) is abundant and non-toxic, but is understudied compared to other metals. In this project a series of of reactive maganese complexes are prepared and their basic reactions explored. Based on these results new manganese catalysts for a variety of processes are designed. The project also contains an integrated educational component that emphasizes hands-on experiences for high school students in the local area. This effort aims to assist local schoolteachers in stimulating student enthusiasm in science. Manganese(I) catalysts are currently used in acceptorless (de)hydrogenations with ligand platforms initially designed for ruthenium, but not optimally suited for Mn(I). This project focuses on the preparation of a new library of ligands designed to leverage the special properties of Mn(I). These new ligands include phenol-based phosphines (POP and PO), new PNN and PNP pincer ligands, amino acid-derived chiral PN ligands, and thiophenol-based PS and PSP phosphines. In addition to the synthesis of Mn(I) complexes with these ligands, this research also addresses the lack of Mn(I) catalyst precursors by providing new Mn(I) synthons and/or methods to prepare Mn(I) catalysts from cheaper materials. The electronic properties and decomposition pathways of the Mn(I) complexes and the mechanisms of catalysis are explored to assist robust Mn(I) catalyst design.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.