Synthesis and Reactivity of 1,2-Bis(di-iso-propylphosphino)benzene Nickel Complexes: A Study of Catalytic CO2-Ethylene Coupling

The utilization of renewable carbon dioxide resources in the production of commercial chemicals has been at the center of efforts to improve the sustainability of many widely used consumer products. The catalytic coupling of CO2 with ethylene to generate acrylates is one such avenue of research. Despite decades of investigations, catalytic CO2-ethylene coupling has only recently been experimentally demonstrated. The development of a new nickel-based catalyst, 1,2-bis(di-iso-propylphosphino)benzene nickel(0) 1,5-cyclooctadiene, for acrylate production is detailed here. The stoichiometric reactivity of the catalyst toward the CO2, ethylene, and base reagents, as well as the coordination chemistry of likely catalytic intermediates has been examined. Comparative catalytic experiments were used to identify the influence of commonly employed additives, such as metallic zinc and Lewis acidic salts, on the catalytic CO2-ethylene coupling reaction. In addition, catalytic comparisons of the 1,2-bis(di-isopropylphosphino)benzene nickel(0) 1,5-cyclooctadiene species with a similar previously reported catalyst under newly developed conditions afforded turnover numbers greater than 400, an approximately 4-fold increase over the highest activity reported to date. Significantly, the catalytic trials reveal that small changes in the catalytic conditions and additives can have substantial effects on productivity and that these influences are not uniform with respect to catalyst platforms.