Oligocationic, Ammonium-Functionalized Triarylphosphine Ligands: Coordination Chemistry and Application in Homogeneous Catalysis

Abstract

The work described in this thesis has led to a thorough characterization of hexacationic Dendriphos phosphine ligands as well as of their oligocationic and neutral derivatives, in terms of their steric and electronic properties, their coordination chemistry with respect to transition metals and their performance in transition metal-catalyzed reactions. By varying the number of ammoniomethyl groups in the ligand structure, as well as the size of the substituents at the ammoniomethyl groups, the steric and electronic properties of these ligands can be fine-tuned. Importantly, the presence of multiple permanent cationic charges in the ligand structure leads to a Coulombic repulsion between ligand molecules. The consequences of these effects on the behavior of these ligands in two synthetically highly important catalytic reactions, i.e. the Pd-catalyzed Suzuki-Miyaura cross-coupling reaction and the Rh-catalyzed hydroformylation reaction, have been investigated. The structure-activity relations with respect to this family of ligands that have been established, may be extended to other ligand systems, and as such this work contributes to the knowledge available to the chemical community concerning the rational design of new ligand systems for homogeneous catalysis.