Mechanistic Details of Nickel(0)-Assisted Oxidative Coupling of CO₂ with C₂H₄

The mechanism of the experimentally observed formation of the five-membered nickela−carboxylate complex in the nickel(0)-assisted oxidative coupling of CO2 and C2H4 is revealed by means of density functional calculations. The reliability of the applied DFT methodology has been first assessed by comparison to high-level coupled-cluster calculations on a relevant model reaction. The most important stationary points on the potential energy surface associated with the title reaction have been located, and low-energy reaction pathways have been identified. We show that the C−C bond formation occurs in a single step by the reaction of a nickel−ethylene complex with an incoming CO2 molecule. The solvent effect and the influence of the ancillary ligands on the reaction energetics are examined, and both are shown to be important in these reactions.