Electrochemical N2 splitting at well-defined metal complexes

In this short review, we discuss recent examples of well-defined metal complexes capable to split dinitrogen electrochemically. Large progress has been made in the chemical dinitrogen splitting with molecular complexes during the last couple of years; however, electrochemical N₂ splitting remains scarce. Herein, three distinct examples, which were investigated in depth, are discussed. The iron complex 2⁺ converts N₂ to ammonia via an associative mechanism. With the rhenium pincer complex 3, N₂ is cleaved via a dissociative mechanism forming a very stable Re^V-nitride complex. The aluminium complex 6 also converts N₂ electrochemically to ammonia; however, the mechanism is distinctly different to that in 2⁺ or 3, as there is no evidence for a metal–N₂ interaction and likely the ligand acts as a hydride donor.