A series of bis(mu-oxo)dirhenium complexes, [Re-2(mu-O)(2)(L)(2)](PF6)(n) (L = tris(2-pyridylmethyl)amine (tpa), n = 3 (1) n = 4 (1a); L = ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Metpa), n = 3 (2), n = 4 (2a); bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), n = 3 (3), n = 4 (3a)), have been prepared and characterized by several physical methods. X-ray crystallographic studies for 2, 2a . 2CH(3)CN . 2H(2)O (2a’), and 3a’ (ReO4- salt), include the first structural determinations of (i) the bis(mu-oxo)-(ReReIV)-Re-III complex (2) and (ii) the pair of (ReReIV)-Re-III and Re-2(IV) complexes (2 and 2a’). All the complexes have a centrosymmetric structure, suggesting that the mixed-valence state 2 is of structurally delocalized type. The Re-Re distances for 2, 2a . 2CH(3)CN . 2H(2)O, and 3a’ are 2.426(1), 2.368(1), and 2.383(1) Angstrom, respectively, being consistent with the bond order of 2.5 (sigma(2) pi(2) delta(2) delta*) for 2 and 3 (sigma(2) pi(2) delta(2)) for the others. Methyl substitution on the pyridyl moiety of the ligands has no significant influence to the overall structure.