Theoretical Study on the Rhodium-Catalyzed Electrochemical C–H Phosphorylation: Insights into the Effect of Electro-oxidation on the Reaction Mechanism

The merging of transition-metal-catalyzed C–H bond activation with electro-oxidation has evolved into an appealing protocol for oxidative C–H bond functionalization. Nevertheless, specific effects of the electro-oxidation process on the reaction mechanism of transition-metal catalysis have rarely been investigated. Herein, we present a comprehensive computational study on the rhodium-catalyzed electrochemical C–H phosphorylation of 2-phenylpyridine by diphenylphosphine oxide to reveal the mechanistic details. The effects of electro-oxidation on the three major chemical processes, i.e., C–H activation, P–H activation, and reductive elimination/C–P bond formation, were thoroughly addressed by considering the chemical steps at the Rh(III), Rh(IV), and Rh(V) oxidation states. The calculations demonstrated that the C–H activation prefers to take place at the Rh(III) state, P–H activation at the Rh(IV) state, and reductive elimination at the Rh(V) state. Without electrochemical oxidation, the total barrier for the reductive elimination occurring at the Rh(III) center is unsurmountable under the experimental temperature. The mechanistic insights disclosed in the present study are expected to be beneficial in understanding the transition-metal-catalyzed electro-oxidative C–H bond functionalization.