Electrocatalytic oxidation of methanol by the [Ru3O(OAc) 6(py)2(CH3OH)]3+ cluster: Improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system

Abstract

The [Ru3O(Ac)6(py)2(CH3OH)] + cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/ Ru3III,III,III/Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two Ru IV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states.