Reactivity of Dimeric P/Al-Based Lewis Pairs toward Carbon Dioxide and tert-Butyl Isocyanate

The methylene-bridged phosphinoalane tBu₂PCH₂AlMe₂ exists as a stable, dimeric Lewis adduct, which reacts with carbon dioxide and tert-butyl isocyanate at room temperature, forming five-membered heterocycles; we explored the reaction pathways of these heterocycles with computational chemistry. A carboxylate dimer results when excess carbon dioxide is used. A novel mechanism is presented for this process that presumes the cooperative effect of two CO₂ molecules in which the FLP captured CO₂ is expelled on insertion of a second molecule into the Al–C bond of the initial heterocycle.