Paramagnetic ruthenium(III) complexes bearing O,O chelating ligands: Synthesis, spectra, molecular structure and electron transfer properties

Paramagnetic Ru(III) complexes of the type [RuX2(EPh3)2(L)] (where X = Cl or Br; E = P or As; L = monobasic bidentate benzophenone ligand) have been synthesized from the reaction of ruthenium(III) precursors, viz. [RuX3(EPh3)3] (where X = Cl, E = P; X = Cl or Br, E = As) or [RuBr3(PPh3)2(CH3OH)] and substituted hydroxy benzophenones in a 1:1 molar ratio in benzene under reflux for 6 h. The hydroxy benzophenone ligands behave as monoanionic bidentate O,O donors and coordinate to ruthenium through the phenolate oxygen and ketonic oxygen atoms, generating a six-membered chelate ring. The compositions of the complexes have been established by analytical and spectral (FT-IR, UV–Vis, EPR) and X-ray crystallography methods. The single crystal structure of the complex [RuCl2(PPh3)2(L1)] (1) has been determined by X-ray crystallography and indicates the presence of a distorted octahedral geometry in these complexes. The magnetic moment values of the complexes are in the range 1.75–1.89 μB, which reveals the presence of one unpaired electron in the metal ion. EPR spectra of liquid samples at liquid nitrogen temperature (LNT) show a rhombic distortion (gx ≠ gy ≠ gz) around the ruthenium ion. The complexes are redox active and display quasi-reversible oxidation and quasi-reversible reduction waves versus Ag/AgCl.

Ruthenium(III) benzophenone complexes of the type [Ru(L)X2(Eh3)2] (where X = Cl or Br; E = P or As; L = monobasic bidentate benzophenone ligand) were synthesized and characterized. X-ray diffraction study confirms an O,O coordination mode. All the complexes are paramagnetic and are redox active.Figure optionsDownload as PowerPoint slideHighlights
► New air stable paramagnetic Ru(III) benzophenone complexes were synthesized.
► The structure of one of the complexes was determined by X-ray methods.
► Ru(III) complexes are reported in view of catalytic and biological applications.