Discrete and Monodimensional Heteropolynuclear Structures Formed by Tetracarboxylatodiruthenium(II,III) and Perrhenato Fragments

Reaction between cationic units of carboxylate-bridged diruthenium complexes [Ru₂(μ-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 Ru₂(μ-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 [Ru₂(μ-O₂CPh)₄]⁺ with NBu₄ReO₄ also affords the compounds Ru₂(μ-O₂CPh)₄(ReO₄)(H₂O) (8) and NBu₄[Ru₂(μ-O₂CPh)₄(ReO₄)₂] (9) depending on the reaction conditions. The structure of 8 consists of cationic and anionic units, [Ru₂(μ-O₂CPh)₄(H₂O)₂]⁺ and [Ru₂(μ-O₂CPh)₄(ReO₄)₂]^-, linked by hydrogen bonds, which give a three-dimensional net. The structure of complex 9·0.5H₂O has an anionic unit similar to that of 8, whose counterion is NBu₄⁺. The Ru−Ru bond distances are slightly longer in [Ru₂(μ-O₂CPh)₄(ReO₄)₂]^- than in the polymeric compounds Ru₂(μ-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 ZFS effect using the Hamiltonian _D = SDS. The weak antiferromagnetic coupling is introduced as a perturbation, using the molecular field approximation.