Design, Identification, and Evolution of a Surface Ruthenium(II/III) Single Site for CO Activation

Ru-II compounds are widely used in catalysis, photocatalysis, and medical applications. They are usually obtained in a reductive environment as molecular O-2 can oxidize Ru-II to Ru-III and Ru-IV. Here we report the design, identification and evolution of an air-stable surface [bipy-Ru-II(CO)(2)Cl-2] site that is covalently mounted onto a polyphenylene framework. Such a Ru-II site was obtained by reduction of [bipy-(RuCl4)-Cl-III](-) with simultaneous ligand exchange from Cl- to CO. This structural evolution was witnessed by a combination of in situ X-ray and infrared spectroscopy studies. The [bipy-Ru-II(CO)(2)Cl-2] site enables oxidation of CO with a turnover frequency of 0.73x10(-2) s(-1) at 462 K, while the Ru-III site is completely inert. This work contributes to the studies of structure-activity relationship by demonstrating a practical control over both geometric and electronic structures of single-site catalysts at molecular level.