STRUCTURAL CHARACTERIZATION OF PYRIDAZINE (PYDZ) ADDUCTS OF MX(2) (M=MN, FE, CO, NI, CU OR ZN X=CL OR BR) - AB-INITIO X-RAY-POWDER DIFFRACTION DETERMINATION OF POLYMERIC [NIX(2)(PYDZ)] COMPLEXES

The pyridazine (pydz) complexes of metal halides MX(2) (M = Mn, Fe, Co , Ni, Cu or Zn; X = Cl or Br) have been prepared, using a reagent mola r ratio of 1:1, and investigated by X-ray powder diffraction methods. The crystal structures (orthorhombic, space group lmma, Z = 4) of [NiC l2(pydz)] and [NiBr2(pydz)] have been determined, ab initio. from labo ratory X-ray powder diffraction data only: [NiCl2(pydz)], a = 7.3758(4 ), b = 6.6069(3) and c = 12.7292(7) Angstrom. [NiBr2(pydz)], a = 7.559 8(9), b = 6.8029(8) and c = 12.905(2) Angstrom. The structures have be en solved by direct methods, and refined by the Rietveld technique dow n to R(profile) values of 0.062 and 0.078, respectively. for 4400 data points collected at room temperature in the-range 17 < 2 theta < 105 degrees. Both compounds consist of infinite polymeric chains of nickel atoms, bridged by X (CI or Br) and pyridazine ligands, showing an oct ahedral arrangement and trans- DDh NiX,N-2, chromophores. The Ni-Cl an d Ni-Br distances are 2.422(1) and 2.560(2) Angstrom, respectively. An alyses of the other species have shown-that the analogues of Mn, Fe an d Co are isomorphous with the nickel compounds. while those of Cu and Zn display different diffraction patterns.