Date of Award
© 2019 Audra J. Woodside. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.
Bachelor of Arts
Chemistry & Biochemistry
Christopher R. Graves
One important challenge in green chemistry is the development of safe and sustainable catalytic systems for molecular transformations that do not rely on precious metals. In this vein, I explore how one can expand the utility of aluminum complexes. Aluminum is a prime choice for such catalytic development as it is relatively inexpensive (less than $2/kg), readily available, and non-toxic. Although there are ample examples of aluminum complexes acting as Lewis-acid catalysts, the lack of readily accessible multielectron redox states leaves aluminum complexes inept in redox-based transformations. In order for aluminum complexes to be used in redox reactions, I prepared complexes that contain redox-active ligands. Specifically, I focused on the synthesis of aluminum complexes implementing a multidentate ligand incorporating three nitroxide (N-O) functional groups, which is known to exist across three oxidation states. It is hypothesized that the Al-nitroxide complex will similarly span several oxidation states. Herein, I report the synthesis (TriNOx³⁻)Al-py, which uses a multidentate redox-active tripodal tris(nitroxide) ligand. Moreover, I report the synthesis of analogous gallium and indium complexes, providing an array of complexes that vary in electronic parameters, steric profiles, and metal ionic radius. The alNo uminum complex exhibits multi-electron electrochemical behavior, and has the ability to participate in metal-ligand cooperative catalysis due to the Lewis acidity of the aluminum center and the Lewis basicity of the nitroxide nitrogens. These characteristics have been exploited in a catalytic system for the hydroboration of carbonyls. Such use of the aluminum complex represents new transition-metal-like reactivity for an earth-abundant metal.
Woodside, Audra J. , '19, "Synthesis and Characterization of Tripodal Tris(nitroxide) Aluminum, Gallium, and Indium Complexes" (2019). Senior Theses, Projects, and Awards. 244.