Lewis Acid Induced β‑Elimination from a Nickelalactone: Efforts toward Acrylate Production from CO2 and Ethylene

The Lewis acid tris­(pentafluorophenyl)­borane was found to rapidly promote ring-opening β-hydride elimination in a 1,1′-bis­(diphenylphosphino)­ferrocene (dppf) nickelalactone complex under ambient conditions. The thermodynamic product of nickelalactone ring-opening was characterized as (dppf)­Ni­(CH­(CH3)­CO2BArf3), the result of β-hydride elimination and subsequent 2,1-insertion from a transient nickel­(II) acrylate hydride intermediate. Treatment of (dppf)­Ni­(CH­(CH3)­CO2BArf3) with a nitrogen-containing base afforded a diphosphine nickel(0) η2-acryl borate adduct. Formation of the diphosphine nickel(0) η2-acryl borate adduct completes a net conversion of nickelalactone to acrylate species, a significant obstacle to catalytic acrylate production from CO2 and ethylene. Displacement of the η2-acrylate fragment from the nickel center was accomplished by addition of ethylene to yield a free acrylate salt and (dppf)­Ni­(CH2CH2).