RUTHENIUM(II) (III) AND OXOVANADIUM(IV) COMPLEXES OF HIGHLY CONJUGATED BETA-DIKETONES AND THEIR MACROCYCLIC SCHIFF-BASE BINUCLEAR COPPER(II) COMPLEXES/

Ruthenium(II) complexes of the general formula [Ru(PPh(3))(2)(L)(L')]C lO4 [L = 2,2'-bipyridine or 1,10-phenanthroline; L' = 2-hydroxy-omega- 4-X-phenylcinnamoylacetophenone] have been prepared by reacting L and L' with Ru(PPh(3))(3)Cl-2 in CH2Cl2. The complexes are diamagnetic and absorb intensely in the visible region, owing to the MLCT transition. Hexacoordinated ruthenium(III) complexes, [RuCl2(PPh(3))(2)(L'-diketo nes. Solutions of ruthenium(III) complexes show rhombic e.s.r. spectra at 77 K, and distortion from the octahedral symmetry has been identif ied from the line spacings. The conjugation in diketones favours rever sibility in Ru-II/III and Ru-III/IV and stabilize ruthenium in differe nt oxidation states owing to d(pi-pi) interaction. Oxovanadyl(IV) com plexes of the beta-diketones with a metal-to-ligand ratio of 1:2 and s quare pyramidal geometry were also prepared. The e.s.r spectra of thes e complexes show the presence of an unpaired electron in the d(xy) orb ital and the hyperfine splitting constants are sensitive to solvent ch ange. A new class of highly conjugated Schiff bases obtained from the above diketones and 2-aminothiophenol behave as dibasic, tridentate li gands in their copper(II) complexes. The subnormal magnetic moments an d hyperfine splittings of these complexes are ascribed to an antiferro magnetic exchange interaction arising from dimerization. Cyclic voltam mograms show that the electron transfer occurs in two steps correspond ing to Cu-II-Cu-I and Cu-I-Cu-I redox states.