Reaction between cationic units of carboxylate-bridged diruthenium complexes [Ru-2(mu-O2CR)(4)](+) (R = Me, CMePh2, CMe3, CH2CH2OMe, C(Me)=CHEt, C6H4-P-OMe, Ph) and tetrabutylammonium perrhenate gives complexes with different arrangements in the solid state, Thus, the compounds Ru-2(mu-O2CR)(4)(ReO4) [R = Me (1), CMePh2 (2), CMe3 (3), CH2CH2OMe (4), C(Me)=CHEt (5), C6H4-P-OMe (6), Ph (7)] have polymeric structures with the diruthenium units linked by perrhenate ligands in the axial positions. The structures of complexes 3-THF and 4 were established by single-crystal X-ray diffraction. The tetrahedral geometry of the ReO4 anion permits the formation of a chain close to the linearity. In contrast to the polymeric chains observed in complexes 1-7, the reaction of [Ru-2(mu-O-2-CPh)(4)](+) with NBu4ReO4 also affords the compounds Ru-2(mu-O2CPh)(4)(ReO4)(H2O) (8) and NBu4[Ru-2(mu-O2CPh)(4)-(ReO4)(2)] (9) depending on the reaction conditions, The structure of 8 consists of cationic and anionic units, [Ru-2(mu-O2CPh)(4)(H2O)(2)](+) and [Ru-2(mu-O2CPh)(4)(ReO4)(2)](-), linked by hydrogen bonds, which give a three-dimensional net, The structure of complex 9-0.5H(2)O has an anionic unit similar to that of 8, whose counterion is NBu4+, The Ru-Ru bond distances are slightly longer in [Ru-2(mu-O2CPh)(4)(ReO4)(2)] than in the polymeric compounds Ru-2(mu-O2CR)(4)-(ReO4). The magnetic behavior owes to the existence of zero-field splitting (ZFS) and a weak antiferromagnetic coupling. The experimental data are fitted with a model that considers the US effect using the Hamiltonian H-D = SDS. The weak antiferromagnetic coupling is introduced as a perturbation, using the molecular field approximation.