Tuning Teflon-Coated Earth-Abundant Metal Complexes in Oxidative Catalysis

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With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Linda Doerrer of Boston University and Professor Kimberly Ann Stieglitz of Roxbury Community College will study the specific conversion of carbon-hydrogen bonds to carbon-oxygen and carbon-carbon bonds. These oxidation reactions are widespread and critical reactions in modern chemistry. The cheapest and most sustainable oxidant is atmospheric oxygen (O2) but oxygen also is capable of oxidatively inactivating many catalyst systems. Almost all catalysts that utilize O2 in these oxidation reactions contain transition metals that enable these reactions to take place. This work will expand on current efforts to prepare new Cu catalysts supported by fluorine-rich “Teflon-coated” ligand systems that provide stability to the molecular catalysts. The researchers will prepare new compounds in which clamping ligands hold metal atoms tightly to control reactivity between O2 and the substrate. The project will also probe oxidations using other metals besides Cu, particularly with Mn and V, and will extend the research to Fe-containing systems. An important thrust will be the development of catalysts that perform well in water and air to make these hydrocarbon oxidation systems more sustainable and environmentally friendly. The broader impacts of this work will involve undergraduate course development, student training, and a productive collaboration between Boston University and Roxbury Community College. Roxbury Community College delivers instruction to a high percentage of students from underserved minority groups; thus this collaborative effort will be directed at increasing diversity, equity, and inclusion in STEM (science, technology, engineering and mathematics) fields. In these studies, Professors Linda Doerrer of Boston University and Kimberly Ann Stieglitz of Roxbury Community College will study the oxidation of C-H bonds. This work builds on prior work of the researchers on Cu/O2 chemistry that has demonstrated the effectiveness of fluorinated alkoxide ligands to make highly reactive species for oxidizing C-H bonds. The nature and degree of encapsulation of redox inert counter cations, specifically K, on the catalytic activity will be investigated. Other counter cations of Li, Na, Rb, and Cs will also be pursued, as will an Fe-based catalysts system which will be accessed via two complementary routes. A Bordwell square approach will be used to generate a proposed {Mn(III)OH} reagent in situ that will be used to probe its thermodynamic properties. Exploration of the scope and optimization of reaction conditions with a benchtop-stable vanadium compound capable of catalytic C-H bond oxidation will be part of a hands-on experimental synthesis and spectroscopy class taught at Roxbury Community College by the collaborative team. This continued collaboration brings together expertise in transition metal complexes (Doerrer) and in organic compound characterization (Stieglitz), and will enhance the training of underrepresented minority students for STEM careers while exposing them to research at an R1 university.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.