Aqueous Persistent Noncovalent Ion-Pair Cooperative Coupling in a Ruthenium Cobaltabis(dicarbollide) System As a Highly Efficient Photoredox Oxidation Catalyst

An original cooperative photoredox catalytic system, [Ru(trpy)(bpy)(HO)][3,3'-Co(1,2-CBH)] (; trpy = terpyridine and bpy = bipyridine), has been synthesized. In this system, the photoredox metallacarborane catalyst [3,3'-Co(1,2-CBH)] () and the oxidation catalyst [Ru(trpy)(bpy)(HO)] () are linked by noncovalent interactions and not through covalent bonds. The noncovalent interactions to a large degree persist even after water dissolution. This represents a step ahead in cooperativity avoiding costly covalent bonding. Recrystallization of in acetonitrile leads to the substitution of water by the acetonitrile ligand and the formation of complex [Ru(trpy)(bpy)(CHCN)][3,3'-Co(1,2-CBH)] (), structurally characterized. A significant electronic coupling between and was first sensed in electrochemical studies in water. The Co redox couple in water differed by 170 mV when had Na as a cation versus when the ruthenium complex was the cation. This cooperative system leads to an efficient catalyst for the photooxidation of alcohols in water, through a proton-coupled electron-transfer process. We have highlighted the capacity of to perform as an excellent cooperative photoredox catalyst in the photooxidation of alcohols in water at room temperature under UV irradiation, using 0.005 mol % catalyst. A high turnover number (TON = 20000) has been observed. The hybrid system displays a better catalytic performance than the separated mixtures of and , with the same concentrations and ratios of Ru/Co, proving the history relevance of the photocatalyst. Cooperative systems with this type of interaction have not been described and represent a step forward in getting cooperativity avoiding costly covalent bonding. A possible mechanism has been proposed.