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

The methylene-bridged phosphinoalane tBu(2)PCH(2)AlMe(2) 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.