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

Abstract

The zwitterionic complex [Cp*IrCl{(MeIm)CHCOO}] (1) efficiently catalyzes the selective hydrosilylation of CO to afford the corresponding silylformate. The best reaction performance has been achieved in acetonitrile at 348 K using HSiMePh. The 1-catalyzed reaction of pyrrolidine with CO and HSiMePh strongly depends on the CO pressure. At low concentration of CO (1 bar) formation of the corresponding silylcarbamate, by insertion of CO 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 CO with pyrrolidine and HSiMePh has been observed, and its role in the formation of 1-formylpyrrolidine rationalized. Moreover, a mechanism for the reaction of CO with hydrosilanes, in the presence and in the absence of amines, based on theoretical calculations has been proposed.