Dinuclear ruthenium nitrido complexes supported by the Klaui's tripodal ligand [CpCo{P(O)(OEt)(2)}(3)](-) (L-OEt(-)) have been synthesized starting the ruthenium-(VI) nitrodo precursor [LOEtRuVI(N)Cl-2] (1). Heating a solution of 1 in CCl4 at reflux, followed by recrystallization from hexane under nitrogen, afforded the mixed-valence ruthenium(V)-ruthenium(IV) mu-nitrido complex [LOEtCl2RuV(mu-N)(RuCl2LOEt)-Cl-IV] (2). The cyclic voltammogram of 2 exhibited reversible couples at 0.19 and 1.13 V versus Cp2Fe+/0, which are assigned as the Ru-V-Ru-V/Ru-V-Ru-IV and Ru-V-Ru-V/Ru-V-Ru-IV couples, respectively. Recrystallization of 2 from Et2O/heptane in air yielded the diamagnetic Ru-IV-Ru-IV complex [H13O6][{(LOEtRuCl2)-Cl-IV}(2)(mu-N)] ([H13O6] [2]), which underwent cation exchange with n-Bu4NOH to give [n-Bu4N] [2]. X-ray diffraction revealed that the complex anions in [H13O6][2] and [n-Bu4N][2] contain linear, symmetric Ru-N-Ru bridges. Treatment of 1 with [eta(6)-p-cymene)(RuCl2)-Cl-II](2) in benzene afforded the tetranuclear ruthenium(IV) complex [LOEtCl2RuIV(mu-N)Ru-IV(H2O)Cl-2] (3) containing symmetric Ru-IV-N-Ru-IV bridges. The reaction of 1 with [Ru-II(H)(Cl)(CO)(PCy3)(2)] (Cy = cyclohexyl) gave the ruthenium(VI)-ruthenium(II) nitrido complex [LOEtCl2RuVI(mu-N)Ru-II(H)Cl(CO)(PCy3)(2)] (4). The observed short Ru-II-N bond distance [1.915(5) angstrom] and high C-O stretching frequency (1985 cm(-1)) in 4 are suggestive of pi interaction between Ru-II and the nitride.