Transition-metal co-ordination compounds of a novel aniline-based pyrazole derivative. X-Ray crystal structures of [NN-bis(3,5-dimethylpyrazol-1-ylmethyl) aminobenzene]-dichlorocobalt(II) and -dibromocopper(II)

Abstract

The synthesis and characterization of transition-metal co-ordination compounds containing the newly synthesized ligand NN-bis(3,5-dimethylpyrazol-1 -ylmethyl)aminobenzene (bdmpab) are described. The compounds have the general formulae [M (bdmpab)X₂](M = Co, Cu, or Zn; X = Cl or Brand M = Co; X = SCN or NO₃) and [Cu₂(bdmpab)(SCN)₃] and have been characterized by several spectroscopic methods and analytical techniques. In some compounds (viz. M = Co or Zn; X = Cl or Br and M = Co; X = SCN or NO₃) bdmpab acts as a bidentate ligand and in others (viz. M = Cu; X = Cl, Br, or SCN) as a tridentate ligand. In all compounds the anions are also bonded. Because of the flexible character of the ligand the preference of the transition-metal ions for specific co-ordination geometries is reflected in the resulting co-ordination compounds. To prove the chelating nature of the ligand, and in particular to find out whether or not the aniline nitrogen is co-ordinated, the crystal structures of two representative examples have been determined. [Co(bdmpab)Cl₂] crystallises in space group Pbca, with a= 8.713(2), b= 17.252(4), c= 27.626(7)Å, and Z= 8. Standard least-squares refinement gave R= 0.031 (R′= 0.028). The cobalt atom has a CoN₂Cl₂chromophore in a distorted tetrahedral geometry. Co–N distances are 2.038(2) and 2.044(2)Å for the pyrazole nitrogens. The Co ⋯ N contact of 3.854(2)Å for the aniline nitrogen is considered as non-co-ordinating. Co–Cl distances are 2.2434(8) and 2.2266(8)Å. [Cu(bdmpab)Br₂] crystallises in space group P2₁/n, with a= 8.742(3), b= 29.408(5), c= 8.522(1)Å, β= 107.77(2)°, and Z= 4. Standard least-squares refinement gave R= 0.025 (R′= 0.026). The copper atom has a CuN₃Br₂ chromophore in a distorted trigonal-bipyramidal geometry. The pyrazole nitrogens occupy the axial positions. Cu-N distances are 1.988(5) and 1.981(5)Å for the pyrazole nitrogens and 2.423(1)Å for the aniline nitrogen. Cu–Br distances are 2.454(1) and 2.414(1)Å.