Strategic Ligand Design as a Route to Complexes for Small Molecule Activation and Catalysis

The choice of both ligand and metal centre plays a critical role in the reactivity of a complex. Notably, several ligands have been designed that do not act as innocent spectators but rather act cooperatively with the metal centre, imparting unique reactivity leading to the generation of a number of new catalytic systems. Herein, the syntheses of a library of metal complexes containing strategically designed ligands are detailed with the primary focus being ligand reactivity. In this context, the syntheses of group 10 complexes containing multidentate N-donor ligands are described. The preparation and reactivity of low valent diimine-Ni complexes with electron deficient alkynes and olefins is explored, and the ability of these ligands to act as electron acceptors is discussed. Similarly, the reactivity of bis-phosphinimine and bis-aminophosphine ligands with palladium is described. The choice of metal precursor is demonstrated to be important in the reactions with the bis-phosphinimine ligand, as partial reduction of the ligand is observed leading to the isolation of a mixed aminophosphine-phosphinimine species. Furthermore, the design of novel multidentate ligand systems containing either aminophosphine or phosphinite functional groups for use as reactive ligands is investigated. The syntheses of group 10, ruthenium and rhodium complexes containing these ligands are described. The reactivity of the ligands is detailed, and catalytic applications are explored with the results demonstrating that the nature of the donor ligands has a dramatic impact on reactivity. Finally, the syntheses of phosphinoamide complexes of zirconium, hafnium and ruthenium are detailed. The ability of the metal and ligand to act cooperatively in the activation of small molecules is investigated, further developing a new paradigm in metal-ligand cooperative reactivity. The application of these complexes in a number of catalytic processes including the dehydrogenation of amine-boranes and the reduction of CO2 is also explored.Ph