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

The P,P-chelated stannylene [(i-Pr2P)(2)N](2)Sn 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.