Cleavaging the extremely strong N-N triple bond in dinitrogen generally requires strong reductants and/or harsh conditions. Even though dinitrogen activation and functionalization has been achieved with several homogeneous transition metal complexes so far, catalytic protocols beyond the formation of ammonia or trimethylsilylamines remain elusive. Moreover, most systems rely on thermal N2 splitting, while photochemical pathways are scarce. Here we describe the synthesis of a thermally stable dinitrogen complex supported by a Rhenium PNP pincer complex and its rare photochemical splitting with visible light into the corresponding nitride complexes. This Re(V) nitride bears a trans ligand which weakens the Re≡N bond and enables the reaction with benzoyl chloride to form benzamide and benzonitrile by 2H+/2e- transfer from the pincer ligand. Subsequent electrolysis in presence of an acid could restore the starting complex. Thus a three-step cycle is demonstrated for N2 to nitrile fixation that relies on electrochemical reduction, photochemical N2-splitting and thermal N-transfer.

Metal-ligand cooperative synthesis of benzonitrile via electrochemical reduction and photolytic splitting of dinitrogen

2019 Spring National Meeting

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