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.