Cyano- and aqua-coordinated diruthenium(III) complexes with oxo-bis(acetato) bridge: Preparation and steric and electronic structures

Hua Xin Zhang*, Kiyoshi Tsuge, Yoichi Sasaki, Masatoshi Osawa, Masaaki Abe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Three new μ-oxo-bis(μ-acetato)diruthenium(III) complexes,trans(μ- O,OH2)-[Ru2(μ-O)(μ-CH3COO) 2(bpy)2(H2O)2][PF6] 2·3H2O ([1][PF6]2· 3H2O; bpy = 2,2′-bipyridine), trans(μ-O,CN)-[{Ru 2(μ-O)(μ-CH3COO)2(bpy)2} 2{μ-Ag(CN)2}{μ-Ag2(CN) 3}][Ag(CN)2][Ag2(CN)3](CH 3CN)4(CH2Cl2) (2), and cis(μ-O,CN)-[Ru2(μ-O)(μ-CH3COO) 2(bpy)2(CN)2]·CH3OH· H2O([3]·CH3OH·H2O), have been prepared and their X-ray crystal structures determined. Whereas [1]2+ and 3 are discrete species, 2 is a polymer in which the Ag-CN groups act as bridges through Ru-CN(or NC)-Ag linkages. The discrete complexes dissolve in common solvents, but 2 is only slightly soluble in acetonitrile and dimethyl formamide (DMF) to give fragmented species (denoted as 2′) in solution. Redox waves of 3 were observed at -0.83 (Epc) and +0.76 V (E 1/2) versus Ag/AgCl in a solution of 0.1 M nBu4NPF 6 in CH2Cl2, which correspond to the Ru 2II,III/Ru2III,III and Ru 2III,III/Ru2III,IV processes, respectively. The corresponding redox couples (E1/2) of [1] 2+ were observed at -0.31 and +0.76 V in 0.1 M NaClO4 aqueous solution. Significantly more negative potentials of the Ru 2II,III/Ru2III,III couple for the two cyano complexes (E1/2 = -0.77 V for 2′) are noted. Complexes [1]2+, 2′, and 3 exhibit strong visible absorption bands at λmax = 566 nm (Ïμ = 12600 M-1 cm-1; in H2O), 636 nm (21000 M-1 cm -1; in acetonitrile), and 558 nm (18000 M-1 cm -1; in H2O), respectively. Density functional theory (DFT) molecular orbital calculations have been carried out for [1]2+, trans(μ-O,CN)-[Ru2(μ-O)(μ-CH3COO) 2(bpy)2(CN)2] (2a, a model compound for 2′), 3, [Ru2(μ-O)(μ-CH3COO) 2(py)6]2+ ([4]2+), and trans(μ-O,py)-[Ru2(μ-O)(μ-CH3COO) 2(bpy)2(py)2]2+ ([5]2+; py = pyridine). It was revealed that the frontier orbitals of these complexes are dominated by the Ru(dπ)-μ-O(pπ) type π systems. For the cyano complexes, energies of these π-type MOs are lifted up by the interaction with CN-, so that the energy difference with the upper bpy π* orbitals becomes smaller. Thus, whereas the visible absorption bands of [1] 2+, [4]2+, and [5]2+ are ascribed to the transitions within the π system metal-to-metal charge transfer (MMCT), those of 2′ and 3 are ascribed to the HOMO-to-ligand π* (bpy) transition metal-to-ligand charge transfer (MLCT) and to the mixture of MMCT and MLCT (HOMO-1 to π*), respectively.

Original languageEnglish
Pages (from-to)5132-5143
Number of pages12
JournalEuropean Journal of Inorganic Chemistry
Issue number33
DOIs
StatePublished - 2011/11

Keywords

  • Bridging ligands
  • Charge transfer
  • Cyano complexes
  • Electronic structure
  • Ruthenium

ASJC Scopus subject areas

  • Inorganic Chemistry

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