Comparative Study of Ruthenium(II) and Ruthenium(III) Complexes with the Ligand dmbpy (dmbpy = 4, 4′‐Dimethyl‐2, 2′‐bipyridine)

Abstract

AbstractThe complex cis‐[RuIII(dmbpy)2Cl2](PF6) (2) (dmbpy = 4, 4′‐dimethyl‐2, 2′‐bipyridine) was obtained from the reaction of cis‐[RuII(dmbpy)2Cl2] (1) with ammonium cerium(IV) nitrate followed by precipitation with saturated ammonium hexafluoridophosphate. The 1H NMR spectrum of the RuIII complex confirms the presence of paramagnetic metal atoms, whereas that of the RuII complex displays diamagnetism. The 31P NMR spectrum of the RuIII complex shows one signal for the phosphorus atom of the PF6– ion. The perspective view of each [RuII/III(dmbpy)2Cl2]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 RuIII is 1.3° wider than that in the RuII. The dihedral angles between pair of planar six‐membered pyridyl ring in the dmbpy ligand for the RuII are 4.7(5)° and 5.7(4)°. The observed inter‐planar angle between two dmbpy ligands in the RuII is 89.08(15)°, whereas the value for the RuIII is 85.46(20)°.