Investigation of main group promoted carbon dioxide reduction

Abstract The reduction of carbon dioxide (CO 2 ) is of interest to the chemical industry, as many synthetic materials can be derived from CO 2 . To help determine the reagents needed for the functionalization of carbon dioxide this experimental and computational study describes the reduction of CO 2 to formate and CO with hydride, electron, and proton sources in the presence of sterically bulky Lewis acids and bases. The insertion of carbon dioxide into a main group hydride, generating a main group formate, was computed to be more thermodynamically favorable for more hydridic (reducing) main group hydrides. A ten kcal/mol increase in hydricity (more reducing) of a main group hydride resulted in a 35% increase in the main group hydride's ability to insert CO 2 into the main group hydride bond. The resulting main group formate exhibited a hydricity (reducing ability) about 10% less than the respective main group hydride prior to CO 2 insertion. Coordination of a second identical Lewis acid to a main group formate complex further reduced the hydricity by about another 20%. The addition of electrons to the CO 2 adduct of t Bu 3 P and B(C 6 F 5 ) 3 resulted in converting the sequestered CO 2 molecule to CO. Reduction of the CO 2 adduct of t Bu 3 P and B(C 6 F 5 ) 3 with both electrons and protons resulted in only proton reduction.