Ruthenium(II/III) mediated transformation of 1,2-bis(2′-pyridylmethyleneimino)benzene (L) to 2-(2′-benzimidazolyl)pyridine (L′H) and its in situ formed complexes with Ru(II): X-ray structure of trans-[Ru(PPh3)2(L′H)2](ClO4)2

A series of ruthenium (II) complexes of formulae trans-[Ru(PPh3)2(L′H)2](ClO4)2 (1), [Ru(bpy)(L′H)2](ClO4)2 (2), [Ru(bpy)2(L′H)](ClO4)2 (3), cis-[Ru(DMSO)2(L′H)2]Cl2 (4), and [Ru(L′H)3](PF6)2 (5) (where L′H = 2-(2′-benzimidazolyl)pyridine) have been synthesized by reaction of the appropriate ruthenium precursor with 1,2-bis(2′-pyridylmethyleneimino)benzene (L). The complexes were characterized by elemental analyses, spectroscopic and electrochemical data. All the complexes were found to be diamagnetic and hence metal is in +2 oxidation state. The molecular structure of trans-[Ru(PPh3)2(L′H)2](ClO4)2 has been determined by the single crystal X-ray diffraction studies. The molecular structure shows that Ru(II) is at the center of inversion of an octahedron with N4P2 coordination sphere. The ligand acts as a bidentate N,N′donor. The electronic spectra of the complexes display intense MLCT bands in the visible region. Cyclic voltammetric studies show quasi-reversible oxidative response at 0.99–1.32 V (vs Ag/AgCl reference electrode) due to Ru(III)/Ru(II) couple.