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.