Effects of Weak-Metal Interactions in Ligand-Bridged Complexes of Ruthernium. Dimeric Complexes Containing Ruthenium Ions in Different Coordination Environments.

摘要

The preparation and characterization of the salts ((NH3)5Ru(L)RuCl(bipy)2)(PF6)3(L = pyrazine (pyz),4,4-bipyridine (4,4-bipy),trans-1,2-bis(4-pyridyl)ethylene (BPE), and 1,2-bis(4-pyridyl)ethane(BPA)) are described. The 3+ dimeric ions undergo a reversible one-electron oxidation either chemically or electrochemically in acetonitrile giving the mixed-valence (Ru(III)-Ru(II)) ions, ((NH3)5Ru(L)RuC1(bipy)2)(4+). In the mixed-valence ions, the site of oxidation is largely localized on the (NH3)5Ru-group. The twice-oxidized 5+ ions have also been shown to exist in solution using electrochemical methods. For the ions where the bridging ligand has an intact pi system (pyz,4,4-bipy, or BPE), the effects of weak metal-metal interactions are observed in spectral and reduction potential data and in the appearance of intervalence transfer bands for the mixed-valence ions. With BPA as the bridging ligand, the N-heterocyclic pi systems are separated by the saturated CH2 CH2-linkage, and no evidence for metal-metal electronic interactions has been obtained. From the properties of the intervalence transfer band for the mixed-valence pyrazine-bridged dimer, it can be estimated that electronic interactions in the ground state are lower by a factor of 3 than for the Creutz and Taube ion, ((NH3)5Ru(pyz)Ru(NH3)5)()+). (Author)