Electronic effects of the substituent group in 8-quinolinolato ligand on geometrical isomerism for nitrosylruthenium(II) complexes

The reaction of hydrous nitrosylruthenium trichloride with 2-chloro-8-quinolinol (H2cqn) or 2-methyl-8-quinolinol (H2mqn) in ethyl alcohol, 50 vol.% ethyl alcohol–water, water or acetic acid solution adjusted to pH 5.5 and the reaction of two kinds of geometrical isomers, cis-1 and cis-2[RuX(qn)2NO] (X=acetate or Cl; Hqn=H2cqn or H2mqn), with chloride or acetate ion in ethyl alcohol were examined in order to compare the effect of the chloro and methyl groups of the 2-position in 8-quinolinolato ligands on geometrical isomerism for nitrosylruthenium(II) complexes. The thermal and photoinduced reactions for the 2cqn complexes were also compared with those for the 2mqn complexes. The differences in the substituent in the 8-quinolinolato ligand and of the solvents used for the reactions were related to geometrical isomerism of the products. In general, the 2cqn complexes especially favor the cis-2 geometry, while the 2mqn complexes favor the cis-1 and trans geometries. The structures of cis-1[RuCl(2cqn)2NO], cis-2[RuCl(2cqn)2NO] and trans-[Ru(OEt)(2mqn)2NO] (OEt=ethanolate ion) were determined by X-ray diffraction.