Homogeneous hydrogenation of aqueous hydrogen carbonate to formate under mild conditions with water soluble rhodium(I)- and ruthenium(II)-phosphine catalysts

Water-soluble rhodium(I)- and ruthenium(II)–tertiary phosphine complexes with meta-monosulphonated triphenylphosphine (TPPMS) and 1,3,5-triaza-7-phosphaadamantane (PTA) as ligands catalyze the hydrogenation of aqueous HCO3− to HCO2− under mild conditions. No amine additive is needed for good turnovers. CO2 accelerates the reactions with [RhCl(TPPMS)3] catalyst; however, it slightly inhibits the reductions catalyzed by [RuCl2(TPPMS)2]. Bicarbonate formed in the reaction of limestone with aqueous CO2 can also be used as starting material for formate production.