Molecular Electrochemical Reductive Splitting of Dinitrogen with a Molybdenum Complex

Nitrogen reduction under mild conditions (room T and atmospheric P), using a non‐fossil source of hydrogen remains a challenge. Molecular metal complexes, notably Mo based, have recently been shown to be active for such nitrogen fixation. We report electrochemical N2 splitting with a MoIII triphosphino complex [(PPP)MoI3], at room temperature and a moderately negative potential. A MoIV nitride species was generated, which is confirmed by electrochemistry and NMR studies. The reaction goes through two successive one electron reductions of the starting Mo species, coordination of a N2 molecule, and further splitting to a MoIV nitride complex. Preliminary DFT studies support the formation of a bridging MoIN2MoI dinitrogen dimer evolving to the Mo nitride via a low energy transition state. This example joins a short list of molecular complexes for N2 electrochemical reductive cleavage. It opens a door to electrochemical proton‐coupled electron transfer (PCET) conversion studies of N2 to NH3. N2 splitting is achieved with a simple Mo complex at a carbon electrode. Controlled reduction (a 3 electron transfer process) at −1.4 V (vs. SCE) and ambient conditions (room T and atmospheric P) afforded a Mo nitride complex in 30 % yield. DFT studies support the transient formation of a MoI−N2−MoI bridging dimer.