UC Davis

This dissertation discusses the synthesis and characterization of aluminum(III) (Al3+) complexes with the non-innocent ligands bis(enol)amine (H3ONO) and di(imino)pyridine (I2P). This work contributes to the rich history of main group coordination chemistry by exploring the capacity of these non-innocent ligand Al3+ complexes to activate small molecules through novel ligand-based proton-, electron-, and hydride-transfer reactions. In chapter 2, a series of Al3+ complexes supported by the tridentate bis(enol)amine ligand (H3ONO, 1,1’-azanediylbis(3,3-dimethylbutan-2-one) is coordinated to Al are synthesized and characterized. Reaction of AlCl3 with singly deprotonated H2ONO- affords the pseudo-octahedral complex [(H2ONO-)2Al][AlCl4] (2.1). Reaction of AlCl3 with the doubly protonated HONO2- affords the five-coordinate, pseudo-trigonal bipyramidal complex (HONO2-)AlCl(THF) (2.2). Reversible ligand-based protonation/deprotonation of the Al complexes is demonstrated by the deprotonation of 2.1 with ¬Et3N to afford 2.2 and the protonation of 2.2 with HCl to afford 2.1. An attempt to deprotonate 2.2 with tBuOK yielded [(HONO2-)Al](μ-tBuO) (2.3), with no change to the ligand protonation state. An intermolecular C—H bond activation reaction takes place when 2.2 reacts with two equivalents of TEMPO to afford [(HONO2-)Al(TEMPO)(TEMPOH)] (2.4). In Chapter 3, di(imino)pyridine (I2P) Al¬3+ complexes are synthesized and characterized with ancillary unsupported primary phosphido ligands. (I2P2-)AlI reacts with LiP(H)Mes to form (I2P2-)Al(PHMes) (3.1) and (I2P2-)AlI reacts with LiP(H)Ph to form (I2P2-)Al(PHPh) (3.2). Solid-state structures reveal distorted tetrahedral geometry in 3.1 and 3.2 and single bond character in the Al—P bond. Near infrared spectra display low energy absorption bands near 1050 nm that are consistent with pincer ligand – Al charge transfer transitions and metalloaromatic character in the “(I2P2-)Al” fragment of the molecules. The phosphido ligands lie out of the I2P ligand plane by up to 15°, consistent with previous reports where π-donor halide ligands occupy a fourth coordination site on Al. In Chapter 4, an electrochemical characterization of V{N(SiMe3)2}3 (4.1) is presented. During the preparation of 4.1 a discrepancy between the observed violet color and the previously reported brown color prompted further investigation of the compound. As a result, electrochemical measurements are presented to contribute to the characterization of the purple compound.