Crystal structures of trans-Dichloro- and Dibromo-bis(2,6-dimethylpyridine)copper(II)

The crystal structures of the title compounds have been determined at 295(1) K by X-ray diffraction and refined by full-matrix least squares to residuals of 0.045 and 0.067 for 1224 and 1955 ‘observed’ reflections respectively. The compounds are isomorphous (triclinic, P1, Z 1). Dichloro compound: a 8.068(2), b 8.024(2), c 7.646(2) Å, α 93.84(2), β 113.44(2), γ 117.11(2)°. Dibromo compound: a 7.999(2), b 7.921(2), c 7.849(2) Å, α 94.37(2), β 112.85(2), γ 115.99(2)°. The copper atoms are square-planar coordinated with two halide and two base ligands coordinated necessarily trans by virtue of the siting of the molecule on a centre of symmetry. Cu-X, Cu-N are 2.264(2), 2.011(3) (dichloro); 2.425(1), 1.997(4) Å (dibromo). The plane of the lutidine is almost normal to the CuN₂X₂ plane.