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. [ABSTRACT FROM AUTHOR]