Transfer Hydrogenation to Bicarbonate Salts and CO₂ Catalyzed by IrCp*‐Oxyquinolinate Complexes

Abstract CO 2 functionalization to afford beneficial products is one of the current scientific greatest challenges. Amongst all the possible transformations, the synthesis of formic acid from CO 2 is of high interest due to the enormous industrial production of this chemical. Particularly interesting is the obtention of formic acid via transfer hydrogenation (TH) of CO 2 , allowing milder reaction conditions and eliminating the need to employ a hazardous gas as H 2 . Iridium catalysts promoted TH reactions have been widely studied; however, examples of TH to CO 2 are very scarce. In our search for the development of new and more efficient catalysts, we have studied the ability of [IrCp*(QO)X] complexes (QO = 8‐oxyquinolinate) to promote TH to bicarbonate salts and CO 2 to obtain formate salts. The study shows a crucial ligand effect, obtaining the best results when [IrCp*(5,7‐Me,Me‐QO)Cl] was employed. Under optimized conditions, TON values up to 135 and 60 were obtained for TH to bicarbonate salts, and CO 2 , respectively. Remarkably, [IrCp*(5,7‐Me,Me‐QO)Cl] is able to trap and transform atmospheric CO 2 into formate salts.