RUI: Synthesis and Characterization of Group 13 Metal Complexes Designed for the Metal-Ligand Cooperative Activation O-H, N-H, and C-H Bonds

With the support of the Chemical Synthesis (SYN) program in the Division of Chemistry Professor Christopher Graves of Swarthmore College is studying the development of group 13 metal complexes of non-innocent ligands. These complexes will have the ability to participate in metal-ligand cooperative bond-making and breaking of small molecules. The metal-facilitated reactivity of small molecules is of fundamental importance to the synthesis of both fine and commodity chemicals. Conventional coordination complexes of group 13 elements are hallmarked by their redox stability and lack the multi-electron redox chemistry required for chemical transformations dependent on oxidation and reduction upon which small molecule activation is typically built. In this funded work, group 13 metals complexes of non-innocent ligands will be prepared. The complexes are designed to undergo synergistic reactivity with a small molecule and both the metal ion and ligand-based electrons. This metal-ligand-cooperative (MLC) chemistry affords the bond making/breaking the metal cannot achieve alone. Ultimately, our system will offer a new choice for activation of small molecules with Earth-abundant group 13 metals. This pursuit allows undergraduate students to acquire specialized training in the synthesis and characterization of inorganic coordination complexes, as well as in physical inorganic and organic techniques applied to understanding the relativities of those complexes. This research project seeks to develop a complete understanding of the MLC chemistry of the group 13 metal coordination complexes having tripodal nitroxide-based ligand systems, (RTriNOx3–)M, to realize activation of a broad range of H–X (X = O, N, C) bonds. We will prepare (RTriNOx3–)M complexes across all of the group 13 metals (M = B, Al, Ga, In) that systematically incorporate electron-donating/-withdrawing substituents (R) within the ligand framework. We will fully deduce the electronic structures of the (RTriNOx3–)M complexes and will assess their Lewis acidities using a suite of computational and spectroscopic tools. We will then explore the MLC reaction chemistry of the complexes toward the activation of a range of H–O, H–N, and H–C bonds. At the completion of this project we will have developed the key structure-function relationships that underpin productive MLC reactivity of the (RTriNOx)M complexes. 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.