Water Oxidation by In Situ Generated [RuII(OH2)(NCNHCO)(pic)2]+

Graphical Coordination configuration matters : A Ru dimer, [Ru(NC NHC O)(pic) 2 ] 2 2+ ( 2 ), which transforms to two single-site Ru-OH 2 species to initiate water oxidation, was prepared and fully characterized. Complex 2 could catalyze water oxidation electrochemically, chemically and photochemically, exhibiting an excellent reactivity and stability. A dinuclear ruthenium complex [Ru II (NC NHC O)(pic) 2 ] 2 2+ ( 2 ) was firstly prepared and characterized spectroscopically and electrochemically. Instead of the conventional ligand exchange, complex 2 dissociates in situ to afford two single-site Ru aqua complexes, [Ru II (OH 2 )(NC NHC O)(pic) 2 ] + , which mediates water oxidation through proton-coupled electron transfer events. In electrokinetic studies, complex 2 demonstrated a TOF of 150.3 s −1 comparable to those state-of-the-art catalysts at neutral conditions. TONs of 2173 and 217 were attained in chemical and photochemical water oxidation when 2 was used as a catalyst, exhibiting good stability. Notably, a TOF of 1.3 s −1 was achieved at CAN-driven water oxidation, which outperformed most of the reported single-site Ru complexes, indicating that complex 2 is one of most active water oxidation catalysts (WOCs) to date. The unique coordination configuration and outstanding catalytic performance of complex 2 might shed light on the design of novel molecular WOCs.