Metal-Ligand Cooperative Synthesis of Benzonitrile by Electrochemical Reduction and Photolytic Splitting of Dinitrogen

Thermal nitrogen fixation relies on strong reductants to overcome the extraordinarily large N-N bond energy. Photochemical strategies that drive N-2 fixation are scarcely developed. Here, the synthesis of a dinuclear N-2-bridged complex is presented upon reduction of a rhenium(III) pincer platform. Photochemical splitting into terminal nitride complexes is triggered by visible light. Clean nitrogen transfer with benzoyl chloride to free benzamide and benzonitrile is enabled by cooperative 2 H+/2 e(-) transfer of the pincer ligand. A three-step cycle is demonstrated for N-2 to nitrile fixation that relies on electrochemical reduction, photochemical N-2-splitting and thermal nitrogen transfer.