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

The six-coordinate Fe^III-aqua complex [Fe^III(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 Fe^V(O)²⁺ followed by a reaction first order in catalyst and added water, respectively, with k_o = 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.