Mechanistic Insights on the Functionalization of CO2 with Amines and Hydrosilanes Catalyzed by a Zwitterionic Iridium Carboxylate-Functionalized Bis-NHC Catalyst

Article abstract of DOI:10.1002/cctc.201901687

The zwitterionic complex [Cp*IrCl{(MeIm)₂CHCOO}] (1) efficiently catalyzes the selective hydrosilylation of CO₂ to afford the corresponding silylformate. The best reaction performance has been achieved in acetonitrile at 348 K using HSiMe₂Ph. The 1-catalyzed reaction of pyrrolidine with CO₂ and HSiMe₂Ph strongly depends on the CO₂ pressure. At low concentration of CO₂ (1 bar) formation of the corresponding silylcarbamate, by insertion of CO₂ into the Si?N bond of the in situ generated silylamine was observed, while at higher pressure (3 bar) the formamide derivative was obtained as major reaction product. The unexpected formation of pyrrolidin-1-ium formate as intermediate of the reaction the 1-catalyzed of CO₂ with pyrrolidine and HSiMe₂Ph has been observed, and its role in the formation of 1-formylpyrrolidine rationalized. Moreover, a mechanism for the reaction of CO₂ with hydrosilanes, in the presence and in the absence of amines, based on theoretical calculations has been proposed.