Novel pentacoordinated ruthenium(II) complexes with a NNS chelating ligand: Synthesis, characterization and electrochemical studies

Article abstract of DOI:10.1016/S0277-5387(96)00500-1

The NNS chelating donor N-2-mercaptophenyl-(2′-pyridyl)methylenimine (PabtH) reacted with Ru(PPh₃)₃Cl₂ to give a series of ruthenium(II) complexes Ru(Pabt) (PPh₃)X {X = Cl(1), Br(3)}, Ru(Pabt) (PPh₃)₂Cl (2), [Ru(Pabt) (PPh₃)L]ClO₄ {L = 1-Meimz (2a), 2-Meimz (1c)}, [Ru(Pabt) (PPh₃) (L′)₂]ClO₄ {L′ = 1-Meimz (1a), imz (1b), H₂O (1f)} and [Ru(Pabt) (PPh₃) (L-L)]ClO₄ {L-L = bpy (1d), Phen (1e); bpy = 2,2′-bipyridine, Phen = 1,10-phenanthroline}. They have been characterized using IR, UV-vis, {¹H and ³¹P} NMR, EPR, magnetic susceptibility at room temperature, measurement of molecular weight, molecular conductance in solution and elemental analysis. The stabilisation of the pentacoordinated 16-electron complexes (1, 3, 1c and 2a) is attributed to pπ donation by the sulfur atom of the ligand Pabt. Square pyramidal structure is proposed for these pentacoordinated complexes. Electron transfer behaviour of all the complexes has been explored by cyclic voltammetry in CH₂Cl₂ and CH₃CN using TEAP as the supporting electrolyte. The five-coordinated complexes display cathodically shifted oxidation waves in CH₂Cl₂, when TEACl was used as supporting electrolyte. Linear correlation of electrochemical data in terms of Lever's electrochemical parameter E_L and the energy of metal to ligand charge transfer band has been attempted.