Water Oxidation by In Situ Generated [RuII (OH2 )(NCNHC O)(pic)2 ].

A dinuclear ruthenium complex [RuII (NCNHC O)(pic)2 ]22+ (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, [RuII (OH2 )(NCNHC 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.