μ-Halo bridged binuclear ruthenium(III) complexes featuring pyridazine ligands: Synthesis, structure, spectral and electrochemical properties

Abstract

The reaction of [RuX3(AsPh3)3] and N,N-disubstituted pyridazine-3,6-diamine in benzene under reflux afford novel binuclear, halo-bridged, ruthenium(III) complexes with the general formula [Ru2(AsPh3)2(μ-X)2X4(L)] (X=Cl or Br; L=N,N-disubstituted pyridazine-3,6-diamine). All the complexes have been characterized by elemental analysis, spectral (UV–Vis, EPR) and electrochemical methods (CV, DPV). The electronic spectra of the complexes indicate the presence of d–d and intense LMCT transitions in the visible region. The molecular structure of one of the complexes (2) has been determined by X-ray crystallography, which indicates the bridging coordination of the pyridazine in these binuclear complexes. In complex (2) each metal has a distorted octahedral NCl4As coordination sphere constituted by the two exogenous bridging chlorides. The complexes are paramagnetic (low spin, d5) in nature and all the complexes at 77K show rhombic distortion around the ruthenium ion with three different ‘g’ values (gx≠gy≠gz). All the complexes exhibit two quasi-reversible one electron reductive responses (RuIII–RuIII/RuII–RuIII; RuII–RuIII/RuII–RuII) within the E1/2 range of −0.68 to −0.78V and −1.25 to −1.33V, respectively, versus SCE.