Synthesis of £^-Diimine and iminoisoindoline ligands for applications in palladium and aluminum coordination chemistry and catalysis

Abstract

This work began with the synthesis and full characterization of a novel £^-diimine ligand, (2,6-iPr2C6H3N=CH)2C6H4, from the reaction of o-phthaladehyde and the bulky aniline, 2,6-diisopropylaniline. It was observed that any di-ortho-substituted aniline with less bulky groups than isopropyl groups resulted in formation of the corresponding iminisoindolines. Reaction of the £^-diimine ligand with PdCl2 did not result in a seven-membered coordination complex, but in non-palladacyclic complex, [(g-diimine)PdCl(ƒÝ-Cl)]2. Whereas reaction with Pd(OAc)2 gave an S-shaped five-membered trinuclear palladacyclic complex, {1,2-(2,6-iPr2-C6H3N=CH)2-C6H3]Pd(ƒÝ-OAc)2}2Pd. These complexes were found to be active precatalysts for Heck and Suzuki coupling reaction giving TONs of up to 104 and 86, for arylbromides and arylchlorides, respectively.

On the other hand, a series of neutral and cationic seven-membered aluminum coordination complexes were obtained from the reaction of £^-diimine with a variety of aluminum species (AlMe3, AlMe2Cl, AlMeCl2 and AlCl3). The synthesis and characterization of these complexes are exemplified.

Also illustrated in this thesis is the synthesis and characterization of a series of air- and moisture-stable iminoisoindoline-based palladacyclic compounds of the general formula, [(iminoisoindoline)Pd{ƒÝ-OAc}]2. These six-membered palladacyclic complexes were obtained through a simple two-step protocol as analytically pure solids. Phosphine-ligated mononuclear palladacycles of the general formula, [Pd(iminoisoindoline)X(PR3)], X= OAc or Cl, R = Ph or Cy, are also described. Dinuclear palladacycles were also found to be active for the Heck and Suzuki C-C coupling reactions. TONs of up to 106, 105 and 60 were observed for coupling of iodobenzene, p-acetylbromobenzene and p-chlorobenzaldehyde, respectively in the Heck coupling reaction.