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

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 77 K 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 −0.78 V and −1.25 to −1.33 V, respectively, versus SCE.

Binuclear ruthenium(III) pyridazine complexes have been synthesized and characterized (X-ray, UV–Vis, EPR and CV). The bridging coordination nature of the pyridazine was confirmed by a single crystal X-ray study and reveals the presence of a distorted octahedral geometry around ruthenium. All the complexes show two successive quasi-reversible reductions.Figure optionsDownload as PowerPoint slideHighlights
► Novel paramagnetic binuclear ruthenium(III) complexes are synthesized.
► The binucleating nature of pyridazine ligands was confirmed.
► A μ-chloro bridged binuclear ruthenium(III) complex is confirmed by an X-ray study.