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

The reaction of t Bu 2 P(O)H with Bis 2 AlH (Bis = CH(SiMe 3 ) 2 ) afforded the adduct t Bu 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 t Bu 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 t Bu 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.