A FAMILY OF MIXED-LIGAND COMPLEXES OF RU-II-L [L EQUALS N-ARYL-PYRIDINE-2-ALDIMINE], THEIR REACTIONS, ISOLATION AND CHARACTERIZATION - X-RAY CRYSTAL-STRUCTURE OF [RU(PIC)(L(1))(2)][CLO4]CENTER-DOT-CH2CL2 [PIC EQUALS 2-PICOLINATE ION]

Synthesis of the tris-chelated complexes [Ru(L)(n)(L(3))(3-n)](2+) (L = N-aryl-pyridine-2-aldimine, L(3) = 2-(m-tolylazo)pyridine) based on silver(I) assisted trans-metallation is described. The complexes, [Ru( L)(3)](2+) and [Ru(L)(L(3))(2)](2+) afford [Ru(pic)(L)(2)](+) and [Ru( pic)(L(3))(2)](+) (pic = 2-picolinate ion) respectively, on hydrolysis and subsequent oxidation. When RuCl2(L)(2) was reacted with two moles of [Ag(L(3))(2)](+), a pink complex of composition [Ru(L)(L(3))(L(4)) ](+) [L(4) = N-aryl-2-picolinamide] was isolated along with the expect ed brown complex, [Ru(L(3))(L)(2)](2+). Initial oxidation of the metal ion favours L --> L(4) conversion. The complexes have been characteri zed using spectroscopy and X-ray crystallography. The X-ray structure of [Ru(pic)(L(1))(2)]ClO4 . CH2Cl2 is reported. The metal oxidation as well as ligand reductions for the complexes have been studied voltamm etrically 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)(L(3))(2)](+) and [Ru(L)(L(3))(L(4))](+) occur at lower potentials as compared to their parent [Ru(L)(n)(L(3)) (3-n)](2+) complexes. All the complexes show metal-to-ligand charge tr ansfer transitions in the visible range and absorption energies linear ly correlate with the differences between the metal oxidation and the first ligand reduction potentials. (C) 1997 Elsevier Science Ltd.