Carbon dioxide reduction by an Al–O–P frustrated Lewis pair

The reaction of tBu(2)P(O)H with Bis(2)AlH (Bis = CH(SiMe(3))(2)) afforded the adduct tBu(2)P(H)–O–Al(H)Bis(2) (3). It slowly releases H(2) to form the first oxygen-bridged geminal Al/P frustrated Lewis pair tBu(2)P–O–AlBis(2). 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(2). Importantly, the H(2) adduct 3 reduces CO(2) in a stoichiometric reaction leading to the formic acid adduct tBu(2)P(H)–O–Al(CO(2)H)Bis(2). 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.