Carbon dioxide reduction by an Al-O-P frustrated Lewis pair.

The reaction of BuP(O)H with BisAlH (Bis = CH(SiMe)) afforded the adduct BuP(H)-O-Al(H)Bis (3). It slowly releases H to form the first oxygen-bridged geminal Al/P frustrated Lewis pair BuP-O-AlBis. It is capable of reversibly binding molecular hydrogen to afford 3, shown by NMR and H/D scrambling experiments, and forms a 1,2-adduct with CO. Importantly, the H adduct 3 reduces CO in a stoichiometric reaction leading to the formic acid adduct BuP(H)-O-Al(COH)Bis. The formation of the different species was explored by density functional theory calculations which provide support for the experimental results. All products were characterized by NMR spectroscopy as well as X-ray diffraction experiments and elemental analyses.