Electrochemical Conversion of Bicarbonate to Formate Mediated by the Complex RuIII(edta) (edta4- = ethylenediaminetetraacetate)

In this paper, we present the first example of a ruthenium(III) complex, [RuIII(edta)] (edta = ethylenediaminetetraacetate), that catalyzes the electrochemical conversion of hydrogen carbonate to formate selectively. The formation of an [RuIII(edta)(HCO3)]2– species through the reaction of the [RuIII(edta)(H2O)]– catalyst and hydrogen carbonate (HCO3–) was studied kinetically by using the stopped‐flow technique. The value of the second‐order rate constant for the formation of the [RuIII(edta)(HCO3)]2– complex was 82 ± 7 M–1 s–1 at 25 °C and pH = 6.4. Electrochemical reduction of hydrogen carbonate (HCO3–) was achieved by carrying out constant‐potential bulk electrolysis at –0.4 V (vs. SCE) with a mercury‐pool cathode at pH = 6.4. The formation of formate as the only reduction product was evidenced by a 13C NMR analysis of the reaction mixture obtained after electrolysis. [RuIII(edta)(H2O)]– (edta = ethylenediaminetetraacetate) mediates the electrochemical conversion of hydrogen carbonate to formate through the formation of an [RuIII(edta)(HCO3)]2– species, which undergoes electrochemical reduction at –0.4 V (vs. SCE) at a mercury‐pool cathode at pH = 6.4. This results in the formation of formate as the only product.