A family of mixed ligand complexes of Ru^II-L [L=N-aryl-pyridine-2-aldimine], their reactions, isolation and characterization. X-ray crystal structure of [Ru(pic)(L¹)₂][ClO₄]. CH₂Cl₂ [pic= 2-picolinate ion]

Abstract

Synthesis of the tris-chelated complexes [Ru(L)_n(L³)_3-n]²⁺ (L=N-aryl-pyridine-2-aldimine, L³=2-(m-tolylazo)pyridine) based on silver(I) assisted trans-metallation is described. The complexes, [Ru(L)₃]²⁺ and [Ru(L)(L³)₂]²⁺ afford [Ru(pic)(L)₂]+ and [Ru(pic)(L³)₂]⁺ (pic= 2-picolinate ion) respectively, on hydrolysis and subsequent oxidation. When RuCl₂(L)₂ was reacted with two moles of [Ag(L³)₂]⁺, a pink complex of composition [Ru(L)(L³)(L⁴)]⁺ [L⁴=N-aryl-2-picolinamide] was isolated along with the expected brown complex, [Ru(L³)(L)²]²⁺. Initial oxidation of the metal ion favours L→L⁴ conversion. The complexes have been characterized using spectroscopy and X-ray crystallography. The X-ray structure of [Ru(pic) (L¹)₂]ClO₄.CH₂Cl₂ is reported. The metal oxidation as well as ligand reductions for the complexes have been studied voltammetrically in acetonitrile using platinum as the working electrode. It has been observed that the oxidation of the transformed complexes, viz. [Ru(pic) (L)₂]⁺, [Ru(pic)(L³)₂]⁺ and [Ru(L)(L³)(L⁴)]⁺ occur at lower potentials as compared to their parent [Ru(L)_n(L³)_3-n]²⁺ complexes. All the complexes show metal-to-ligand charge transfer transitions in the visible range and absorption energies linearly correlate with the differences between the metal oxidation and the first ligand reduction potentials.