Figure 2. A possible reaction pathway by 1.

(a) Protonation of a terminal dinitrogen ligand in 1 followed by exchange of the dinitrogen ligand trans to the NNH group for OTf group. Protons and electrons are supplied by lutidinium and cobaltocene, respectively. Energy changes and activation energies (in parenthesis) for individual reaction steps were calculated at the B3LYP*/BS2 level of theory (units in kcal mol⁻¹). NB represents that the corresponding reaction has no activation barrier. (b) A sequential protonation/reduction of IV and separation of bimetallic complexes leading to formation of ammonia and the monometallic nitride complex XI. (c) A sequential protonation/reduction of XI via the six-coordinate imide complex XIII to give the ammonia complex XV. (d) Ligand exchange of ammonia for molecular dinitrogen leading to regeneration of 1.