Generation of a Doubly Bridging CO₂ Ligand and Deoxygenation of CO₂ by an (NHC)Ni(0) Complex

Abstract

The treatment of [(IPr)Ni(μ-Cl)]2 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaOt-Bu and then pinB-Bpin (bis(pinacolato)diboron) gives rise to a mono-NHC−Ni(0) complex, which dimerizes upon crystallization. The same product is prepared by the treatment of [(IPr)Ni(μ-Cl)]2 with Li(BEt)3H, or with NaOt-Bu and then HSi(OEt)3. The treatment of [(IPr)Ni]2 or its monomer with CO2 reduces CO2 to CO generating [(IPr)Ni]2(μ-CO)(μ-η2,η2-CO2). This compound represents an unprecedented symmetric double-bridging mode of CO2