Electrolysis at a mercury cathode controlled at −0.50 V (vs. standard calomel electrode s.c.e.) in a H2SO4–K2SO4electrolyte with pH of 2.6 and saturated with Ar gas has been used to prepare RuII–(NH3)5X. The reaction of this species with N2in the aqueous base electrolyte at 26 °C has been studied and found to follow the equations:In base electrolyte saturated with N2at 1 atm (CN2 ≈ 6 × 10−4 M) the value of the apparent first order constant,k′mis 4.4 × 10−5s−1and the value ofkdis 4.2 × 10−21 mole−1s−1.The electrochemistry of the various ruthenium species was also investigated in the H2SO4–K2SO4electrolyte. At the dropping mercury electrode, RuIII(NH3)5Cl gave a well-defined one electron reduction wave with E1/2 = −0.27 V; RuII(NH3)5X gave a well-defined one electron oxidation wave with E1/2 = −0.25 V. The nitrogen complexes gave oxidation waves at a rotating platinum microelectrode, the monomer with E1/2 = +0.72 V and the dimer with E1/2 = +0.78