Oxidation of Linear Trinuclear Ruthenium Complexes [Ru3(dpa)4Cl2] and [Ru3(dpa)4(CN)2]: Synthesis, Structures, Electrochemical and Magnetic Properties

• Published in: Chemistry : a European journal 2007-01, Vol.13 (5), p.1442-1451
• Main Authors: Kuo, Ching-Kuo, Liu, Isiah Po-Chun, Yeh, Chen-Yu, Chou, Chung-Hsien, Tsao, Ting-Bin, Lee, Gene-Hsiang, Peng, Shie-Ming
• Format: Article
• Language: English
• Subjects: density functional calculations; metal-metal interactions; multiple bonds; N ligands; ruthenium
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200601219

The neutral, monocationic, and dicationic linear trinuclear ruthenium compounds [Ru3(dpa)4(CN)2], [Ru3(dpa)4(CN)2][BF4], [Ru3(dpa)4Cl2][BF4], and [Ru3(dpa)4Cl2][BF4]2 (dpa=the anion of dipyridylamine) have been synthesized and characterized by various spectroscopic techniques. Cyclic voltammetric and spectroelectrochemical studies on the neutral and oxidized compounds are reported. These compounds undergo three successive metal‐centered one‐electron‐transfer processes. X‐ray structural studies reveal a symmetrical Ru3 unit for these compounds. While the metalmetal bond lengths change only slightly, the metalaxial ligand lengths exhibit a significant decrease upon oxidation of the neutral complex. The electronic configuration of the Ru3 unit changes as the axial chloride ligands are replaced by the stronger “π‐acid” cyanide axial ligands. Magnetic measurements and 1H NMR spectra indicate that [Ru3(dpa)4Cl2] and [Ru3(dpa)4Cl2][BF4]2 are in a spin state of S=0 and [Ru3(dpa)4Cl2][BF4], [Ru3(dpa)4(CN)2], and [Ru3(dpa)4(CN)2][BF4] are in spin states of S=1/2, 1, and 3/2, respectively. These results are consistent with molecular orbital (MO) calculations. Changing structures in ruthenium complexes: The one‐ and two‐electron oxidized products of neutral trinuclear ruthenium compounds (shown here) have been synthesized and structurally characterized. The Ru3 unit of these oxidized compounds is in an essentially symmetrical arrangement. The RuLaxial bond lengths and the RuRu distances show significant changes upon oxidation of the neutral triruthenium dichloro and dicyano compounds.