Nitrogen-based ligands for iron, zinc and cobalt catalyzed selective processes

Identificador:  TDX:2815

Handle: https://hdl.handle.net/20.500.11797/TDX2815

Autors:  Mercadé Espinosa, Elisabet

Resum:
This thesis deals with the synthesis of new polydentate ligands, and further coordination with first-row transition metals to form effective catalysts in the asymmetric transfer hydrogenation and asymmetric hydrogenation of ketones and coupling of CO2 with epoxides. In Chapter 3 the synthesis of new chiral PNNP ligands is described. The corresponding iron complexes were obtained in good yields, and their X-ray structures were elucidated. The asymmetric transfer hydrogenation of a variety of ketones was carried out with the PNNP/Fe3(CO)12 catalytic system obtaining moderate to high conversions and enantioselectivities. In Chapter 4 the synthesis of a new family of ligands containing N2O2, N2NH2, N4 and N4 (NH) ligand scaffolds is described. The corresponding zinc complexes were obtained in good yields and their X-ray structures were elucidated. The resulting zinc complexes catalyzed the coupling of CO2 with terminal and internal epoxides, being the zinc-N4 complex the most active of the series. This catalytic system could be also recycled up to five times without significant loss of activity, which demostrated the robustness of the system. Chapter 5 describes the synthesis of C^N^C pincer type ligands. Subsequently, their coordination to cobalt was evaluated, observing the coordination of the cobalt center to the pyridine of the C^N^C ligand maintaining the imidazole moieties uncoordinated. Subsequently the activity of these complexes was studied in the asymmetric hydrogenation of various ketones.