Reaction of LRu ^IIICl ₃ (L = 1,4,7-trimethyl-1,4,7-triazacyclononane) with 1,2-phenylenediamine (opdaH ₂) in H ₂O in the presence of air affords [LRu ^II(bqdi)(OH ₂)(PF ₆) (1), where (bqdi) represents the neutral ligand o-benzoquinone diimine. From an alkaline methanol/water mixture of 1 was obtained the dinuclear species [{LRu ^II(bqdi)} ₂(μ-H ₃O ₂)](PF ₆) ₃ (1a). The coordinated water molecule in 1 is labile and can be readily substituted under appropriate reaction conditions by acetonitrile, yielding [LRu ^II(bqdi)(CH ₃CN)](PF ₆) ₂ (2), and by iodide and azide anions, affording [LRu ^II(bqdi)I](PF ₆)·0.5H ₂O (3) and [LRu(bqdi)(N ₃)](PF ₆)·H ₂O (4), respectively. Heating of solid 4 in vacuum at 160 °C generates N ₂ and the dinuclear, nitrido-bridged complex [{LRu(o-C ₆H ₄(NH) ₂)} ₂(μ-N)](PF ₆) ₂ (5). Complex 5 is a mixed-valent, paramagnetic species containing one unpaired electron per dinuclear unit whereas complexes 1-4 are diamagnetic. The crystal structures of 1, 1a·3CH ₃CN, 3, 4·H ₂O, and 5-3CH ₃CN·0.5-(toluene) have been determined by X-ray crystallography: 1 crystallizes in the monoclinic space group P2 ₁/m, Z = 2, with a = 8.412(2) Å, b = 15.562(3) Å, c = 10.025 Å, and β = 109.89(2)°; 1a·3CH ₃CN, in the monoclinic space group C2/c, Z = 4, with a = 19.858(3) Å, b = 15.483(2) Å, c = 18.192(3) Å, and β = 95.95(2)°; 3, in the orthorhombic space group Pnma, Z = 4, with a = 18.399(4) Å,b = 9.287(2) Å, and c = 12.052(2) Å, 4·H ₂O, in the monoclinic space group P2 ₁/c, Z = 4, with a = 8.586(1) Å, b = 15.617(3) Å, c = 16.388(5) Å, and β = 90.84(2)°; and 5·3CH ₃CN·0.5(toluene), in the monoclinic space group P2 ₁/c, Z = 4, with a = 15.003(3) Å, b = 16.253(3) Å, c = 21.196(4) Å, and β = 96.78(3)°. The structural data indicate that in complexes 1-4 the neutral o-benzoquinone diimine ligand prevails. In contrast, in 5 this ligand has predominantly o-phenylenediamide character, which would render 5 formally a mixed-valent Ru ^IVRu ^V species. On the other hand, the Ru-N bond lengths of the Ru-N-Ru moiety at 1.805(5) and 1.767(5) Å are significantly longer than those in other crystallographically characterized Ru ^IV=N=Ru ^IV units (1.72-1.74 Å). It appears that the C ₆H ₄(NH) ₂ ligand in 5 is noninnocent and that formal oxidation state assignments to the ligands or metal centers are not possible.