Molecular Electrochemical Reductive Splitting of Dinitrogen with a Molybdenum Complex

Abstract

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 Mo^III triphosphino complex [(PPP)MoI₃ ], at room temperature and a moderately negative potential. A Mo^IV 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 Mo^IV nitride complex. Preliminary DFT studies support the formation of a bridging Mo^I N₂ Mo^I 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 .

Keywords: Dinitrogen Reductive Splitting; Electrochemical Reduction of N2; Molybdenum Complex; Nitride Mo Complex.