Electrochemical Conversion of Bicarbonate to Formate Mediated by the Complex Ru III (edta) (edta 4– = ethylenediaminetetraacetate)

In this paper, we present the first example of a ruthenium(III) complex, [Ru III (edta)] (edta = ethylenediaminetetraacetate), that catalyzes the electrochemical conversion of hydrogen carbonate to formate selectively. The formation of an [Ru III (edta)(HCO 3 )] 2– species through the reaction of the [Ru III (edta)(H 2 O)] – catalyst and hydrogen carbonate (HCO 3 – ) was studied kinetically by using the stopped‐flow technique. The value of the second‐order rate constant for the formation of the [Ru III (edta)(HCO 3 )] 2– complex was 82 ± 7 M –1  s –1 at 25 °C and pH = 6.4. Electrochemical reduction of hydrogen carbonate (HCO 3 – ) 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 13 C NMR analysis of the reaction mixture obtained after electrolysis.