Synthesis, properties, and structural characterization of bromo- and iodotetracarboxylatodiruthenium(II,III) compounds

The synthesis and characterization of the compounds [RU2X(mu-O2CPh)(4)](n) [X = Br (1), I (2)] and [Ru2X(mu-O2CC6H4-p-OMe)(4)(H2O)] [X = Br (3) and 1 (4)] is described. The structures of these compounds were determined by single-crystal X-ray diffraction. The molecular structures of [Ru2I(mu-O2CCMePh2)(4)(EtOH)(.)0.5EtOH] (5(.)0.5EtOH) and [Ru2I(mu-O2CCMePh2)(4)(MeOH)-0.5H(2)O] (6(.)0.5H(2)O) are also reported. Complexes 1 and 2 show a zigzag polymeric arrangement with the diruthenium units linked by bromide and iodide ligands, respectively. The molecular nature of compounds 3 and 4 shows the influence of the axial ligand in the arrangement in the solid state, which contrasts with the polymeric structure found in all chlorodiruthenium(II,III) derivatives with arenecarboxylate bridging ligands, The Ru-Ru bond lengths for all complexes range from 2.2756(17) to 2.2906(7) and 2.273(3) to 2.2965(6) Angstrom for the bromide and iodide derivatives, respectively. This study demonstrates that the nature of the axial ligand plays an important role in the arrangement in the solid state and in the electronic properties of the halo-tetracarboxylatodiruthenium(II,III) complexes. Thus, the iodo derivatives show an intense solvatochromism, whereas the solvatochromism is slight in the bromo derivatives and is not observed in the chloro complexes. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.