SYNTHESIS AND CHARACTERIZATION OF 1 2 METAL-COMPLEXES OF THE BIHETEROAROMATIC LIGAND 2-(2'-PYRIDYL)QUINOXALINE-(L) AND THE X-RAY STRUCTURE OF [CUL(2)](PF6)/

The first 1:2 metal complexes of 2-(2'-pyridyl) quinoxaline (L) have b een isolated. The physical and spectroscopic characteristics of the co mpounds [MCl(2)L(2)] (M=Ni, Cu, Cd) and [Cu(1)L(2)](PF6) are described . The structure of the copper(I) complex has been determined by X-ray diffraction methods. Crystals are orthorhombic, space group P-cnb with a=11.014(2), b=12.886(2), c=17.806(4) Angstrom, V=2527.1(9) Angstrom( 3) and Z=4. Refinement of the structure gave a final R factor of 0.046 (R(w)=0.041) for 814 unique reflections having I>2.0 sigma(I). The li gand L acts as a bidentate chelate, the ligated atoms being the pyridi ne nitrogen and the nearest quinoxaline nitrogen. The structure of [Cu L(2)](+) consists of a distorted tetrahedral arrangement around the co pper(I) atom with Cu-N bond lengths of 2.023(6) and 2.059(5) Angstrom, and the N-Cu-N angle of the chelating ligand equal to 80.6(2)degrees. A monomeric trans pseudo-octahedral stereochemistry is assigned for t he [MCl(2)L(2)] complexes.