Unexpected ligand lability in condition of water oxidation catalysis

In the search for rational design of improved water oxidation catalysts, enhanced catalytic activities were reported for single site Ru catalysis with Ru-iodide coordination. As these complexes are not initially capable of proton coupled electron transfer (PCET) and Ru O formation, a proposal was put forward on the generation of catalytically active 7-coordinate Ru species. We tested this hypothesis by EPR and X-ray spectroscopy and found that [Ru II (bpy)(tpy)I] + only serves as a precursor for the formation of [Ru IV (bpy)(tpy) O] 2+ . Upon oxidation with excess of Ce IV the Ru I bond quickly dissociates with the formation of [Ru III (bpy)(tpy)H 2 O] 3+ and [Ru IV (bpy)(tpy) O] 2+ complexes. The catalytic steady state was composed of 95% [Ru IV (bpy)(tpy) O] 2+ species. Thus, introducing the Ru I bond into initial catalysts does not serve to improve catalyst design. This manuscript also shows how EXAFS can directly probe transition metal–halogen interaction for in situ catalysis.