Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO 2 fixation by N -benzyl cyclic guanidine under dry and wet conditions.

The efficient CO2 fixation by N -benzyl cyclic guanidine 1 was achieved by bubbling dry CO2 through CH3 CN at 25 °C for 2 h. In addition, the zwitterion adduct 2 and bicarbonate salt 3 were selectively prepared from 1 under dry (in anhydrous CH3 CN) and wet (in CH3 CN containing an equimolar amount of water for 1 ) conditions, respectively. Both compounds 2 and 3 were isolated as white solids and their structures were characterized in detail by elemental analysis, FTIR-ATR, solid-state NMR, TGA, and DFT calculation. These analytical results obviously revealed the formation of a zwitterion adduct and bicarbonate salt from N -benzyl cyclic guanidine and CO2 . Especially, the zwitterion adduct of the monocyclic guanidine derivative and CO2 was isolated and characterized for the first time.