Comparative study of ruthenium(II) and ruthenium(III) complexes with the ligand dmbpy (dmbpy = 4, 4'-Dimethyl-2, 2'-bipyridine)

摘要

The complex cis-[Ru ~III(dmbpy) _2Cl _2](PF _6) (2) (dmbpy = 4, 4'-dimethyl-2, 2'-bipyridine) was obtained from the reaction of cis-[Ru ~II(dmbpy) _2Cl _2] (1) with ammonium cerium(IV) nitrate followed by precipitation with saturated ammonium hexafluoridophosphate. The ~1H NMR spectrum of the Ru ~III complex confirms the presence of paramagnetic metal atoms, whereas that of the Ru ~II complex displays diamagnetism. The ~(31)P NMR spectrum of the Ru ~III complex shows one signal for the phosphorus atom of the PF _6 ~- ion. The perspective view of each [Ru ~(II/III)(dmbpy) _2Cl _2] ~(0/+) unit manifests that the ruthenium atom is in hexacoordinate arrangement with two dmbpy ligands and two chlorido ligands in cis position. As the oxidation state of the central ruthenium metal atom becomes higher, the average Ru-Cl bond length decreases whereas the Ru-N (dmbpy) bond length increases. The cis-positioned dichloro angle in Ru ~III is 1.3° wider than that in the Ru ~II. The dihedral angles between pair of planar six-membered pyridyl ring in the dmbpy ligand for the Ru ~II are 4.7(5)° and 5.7(4)°. The observed inter-planar angle between two dmbpy ligands in the Ru ~II is 89.08(15)°, whereas the value for the Ru ~III is 85.46(20)°.