New findings and current controversies in the reaction of ruthenium red and ammonium cerium(iv) nitrate: focus on the precipitated compound

Finding the true catalyst has always been a challenging step toward the exploration, understanding, and design of catalytic systems for water-oxidation reaction. Many homogeneous and heterogeneous transition metal complexes have been reported that can undergo a complete transformation to the true catalysts during water-oxidation reaction. Herein, the transformation of the previously-explored ruthenium red ([(NH3)(5)RuORu(NH3)(4)ORu(NH3)(5)]Cl-6) catalyst in the presence of ammonium cerium(iv) nitrate is reported. For the first time, it is reported that a heterogeneous nano-sized ruthenium-cerium compound is formed by the electrostatic interaction of [(NH3)(5)RuORu(NH3)(4)ORu(NH3)(5)],(6+/7+) nitrate ions, and the products of the reduction of ammonium cerium(iv) nitrate.