Synergistic Ligand Effects in Palladium Catalysis

The role of ligands, as transition-metal complex modifiers, is fundamental in organometallic chemistry and catalysis. These ancillary, often called spectator , ligands have a profound influence on catalyst activity and longevity. In this proposal, very specific ligand classes, namely the classical P-donors (PR3, P(OR)3, PR(OR)2, P(R2(OR)) in combination with the more recently employed and developed N-Heterocyclic carbenes (NHC) are proposed as synergistic partners enabling established and novel transformations. Systems targeted for study include palladium-based mixed ligand systems for cross-coupling reactions. Proof of concept experiments in this area have been conducted and validate the initial hypothesis of mixed ligand effects on catalyst longevity. Various architectures surrounding palladium are proposed for synthetic and catalytic investigation. Further palladium systems are proposed for investigation in hydrogenation and transfer hydrogenation of various important substrates. It should be noted that such hydrogenations mediated by palladium are rare as reduction to palladium black is often problematic. These initial experiments validate the synergistic effect proposed here for further investigation. The development of systems enabling asymmetric transformations is especially targeted. Applications in aerobic oxidation reactions are also envisaged.