Development of N-Heterocyclic Carbene Transition Metal Catalysts for the Synthesis of Acrylates from Carbon Dioxide and Ethylene

Abstract

The direct carbon dioxide (CO2)-ethylene coupling reactions for the synthesis of acrylic acid salts, which is one of the value-added chemicals, are emerging concerns in the area of carbon capture and utilization (CCU). In 2014, despite the thermodynamic obstacles for catalytic cycles, Limbach and Vogt groups suggested the first one-pot catalytic systems achieved by cleaving the metallalactones using either hard Lewis acid or strong alkoxide bases, respectively. In the ligand point of view, chelating bisphosphine ligands with strong electron density have been mainly efficient in these reactions. Studies on catalysts and reaction conditions result in the best catalytic reactivity (TON 514 with Pd(PPh3)4/dcpe). Recently, bidentate N-heterocyclic carbene (NHC) ligands have started to be explored in these reactions owing to their strong electron-donating character. However, to date, the catalytic performance is very low for the industrial application. Therefore, it is necessary to investigate numerous catalytic systems. For these reasons, in this thesis, several ligands were designed for the direct CO2-ethylene coupling reactions as follows: (1) Pyridine-chelated imidazo[1,5-a]pyridine NHC ligands; (2) Imidazo[1,5-a][1.10]phenanthroline NHC ligands; (3) Triphenylphosphine functionalized bidentate NHC ligands.