Formation of a Reversible, Intramolecular Main-Group Metal–CO₂ Adduct

The P,P-chelated stannylene [(i-Pr2P)2N]2Sn takes up 2 equiv of carbon dioxide (CO2) to form an unusual product in which CO2 binds to the Sn and P atoms, thus forming a six-membered ring complex. Gentle heating of the solid product releases CO2, indicating that CO2 is bound as an adduct to the main-group complex. The groups bound to the CO2 fragment are not particularly sterically crowded or highly acidic, thus indicating that “frustrated” Lewis acid–base pairs are not required in the binding of CO2 to main-group elements.