2-(2'-THIENYL)PYRIDINE VERSUS 2,2'-BIPYRIDYL BINDING MODE IN COPPER(II) COMPLEXES

2-(2'-Thienyl)pyridine (pyth) and its acetylated derivative (apyth) (III) react with copper chloride to give compounds of formulae [Cu(pyth)2Cl2] (I) and [Cu(apyth)2Cl2] (H). The crystal structures of I, II and III have been determined by X-ray methods. In both cop er complexes the metal atom is surrounded by two N atoms (Cu-N, 2.025(5) angstrom in I and 2.021(2) angstrom in H) from two ligands molecules and two Cl atoms (2.265(2) angstrom in I and 2.264(1) angstrom in II) in a typical square planar environment. Two thiophene S atoms (Cu-S, 2.968(2) angstrom in I and 2.904(1) angstrom in II) complete the coordination sphere, making the complex elongated octahedral. By contrast, in all complexes of general formula [Cu(bipy)2X]X, (bipy=2,2'-bipyridyl) the coordination environment around copper is quasi-trigonal bipyramidal, the pyridine rings in each bidentate ligand being almost coplanar, and one anion does not participate to coordinative bonding.