Electrocatalytic Water Oxidation by a Monomeric Amidate-Ligated Fe(III)–Aqua Complex

The six-coordinate FeIII-aqua complex [FeIII(dpaq)­(H2O)]2+ (1, dpaq is 2-[bis­(pyridine-2-ylmethyl)]­amino-N-quinolin-8-yl-acetamido) is an electrocatalyst for water oxidation in propylene carbonate–water mixtures. An electrochemical kinetics study has revealed that water oxidation occurs by oxidation to FeV(O)2+ followed by a reaction first order in catalyst and added water, respectively, with ko = 0.035(4) M–1 s–1 by the single-site mechanism found previously for Ru and Ir water oxidation catalysts. Sustained water oxidation catalysis occurs at a high surface area electrode to give O2 through at least 29 turnovers over an 15 h electrolysis period with a 45% Faradaic yield and no observable decomposition of the catalyst.