Photoelectrochemical Conversion of Dinitrogen to Benzonitrile: Selectivity Control by Electrophile‐ versus Proton‐Coupled Electron Transfer

• Published in: Angewandte Chemie International Edition 2022-08, Vol.61 (35), p.e202205922-n/a
• Main Authors: Fritz, Maximilian, Rupp, Severine, Kiene, Ciara I., Kisan, Sesha, Telser, Joshua, Würtele, Christian, Krewald, Vera, Schneider, Sven
• Format: Article
• Language: English
• Subjects: Ammonia; Benzonitrile; Benzoylation; Conversion; Electrochemistry; Electron transfer; N2 Fixation; Nitrides; Nitrogen fixation; Nitrogenation; Photochemistry; Protons; Reaction Mechanisms; Reduction; Rhenium; Selectivity; Thermochemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202205922

Nitride complexes are key species in homogeneous nitrogen fixation to NH3 via stepwise proton‐coupled electron transfer (PCET). In contrast, direct generation of nitrogenous organic products from N2‐derived nitrides requires new strategies to enable efficient reductive nitride transfer in the presence of organic electrophiles. We here present a 2‐step protocol for the conversion of dinitrogen to benzonitrile. Photoelectrochemical, reductive N2 splitting produces a rhenium(V) nitride with unfavorable PCET thermochemistry towards ammonia generation. However, N‐benzoylation stabilizes subsequent reduction as a basis for selective nitrogen transfer in the presence of the organic electrophile and Brønsted acid at mild reduction potentials. This work offers a new strategy for photoelectrosynthetic nitrogen fixation beyond ammonia—to yield nitrogenous organic products. A new strategy for the conversion of N2 to benzonitrile within a simple two‐step cycle is demonstrated. Photoelectrochemical, reductive splitting of N2 is mediated by a Re pincer complex. The resulting ReV nitride undergoes electrochemical N‐atom transfer in the presence of benzoyl bromide and acid at mild potentials. The high selectivity with respect to nitrile formation is attributed to the unfavorable thermochemistry of proton‐coupled electron transfer (PCET) to the nitride.