A pyrazole derivative of aminoethane as a tridentate chelating ligand towards transition metals. The X-ray structure of [N,N-bis(pyrazol-1-ylmethyl)aminoethane]dibromocopper(II)

Abstract

The syntheses and characterization of transition-metal co-ordination compounds containing the newly synthesized ligand N,N-bis(pyrazol-1-ylmethyl)aminoethane (bpae) are described. The compounds have the general formula [M(bpae)X₂](M = Co, Cu, Zn, or Cd; X = Cl, Br, or NO₃; M = Ni, X = NO₃) and [M (bpae)₂]X₂(M = Mn, Fe, Co, Ni, Cu, Zn, or Cd; X = BF₄; M = Ni or Cu, X = NO₃). The compounds have been characterized through their spectra and solution conductance. The coordination geometries have been deduced to be five-co-ordinate and octahedral. The crystal structure of the green compound [Cu (bpae) Br₂] has been determined by X-ray analysis. A monoclinic unit cell with space group P2¹/c, a= 9.500(5), b= 11.142(4), c= 13.897(8)Å, β= 93.58(8)°, and Z= 4 was found. The copper atom has a N₃Br₂ chromophore in a distorted square-pyramidal geometry. The apical bromide has a distance of 2.6721(5)Å to the copper ion, the equatorial bromide 2.3841(5)Å. Copper–nitrogen distances are 1.940(2) and 1.957(2)Å for the pyrazole nitrogen-donor atoms and 2.1 91(2)Å for the amine nitrogen. This geometry is in accord with the spectroscopic results.