Transition-metal co-ordination compounds containing a novel tridentate pyrazole chelating ligand. X-Ray crystal structure of [NN-bis(3,5-dimethylpyrazol-1-ylmethyl)aminoethane](nitrato-O)-(nitrato-O,O′)nickel (II)

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Abstract
The synthesis and characterization of transition-metal co-ordination compounds containing the newly synthesized ligand NN-bis(3,5-dimethylpyrazol-1-ylmethyl)aminoethane (bdmpae) are described. The compounds have the general formulae [M(bdmpae)X2](M = Co, Ni, Cu, or Zn; X = Cl, Br, or NO3) and [M(bdmpae)2][ClO4]2(M = Co or Ni). The compounds have been characterized by spectroscopic measurements and conductivity studies in solution. In most compounds the ligand behaves as a chelating tridentate ligand. In the mono-adducts the co-ordination around the metal ions is completed by two anions, resulting in a five-co-ordinate geometry (X = Cl or Br) or a six-co-ordinate geometry (X = NO3; in this case one nitrate is monodentate and the other is bidentate). The bis-adducts appear to have distorted octahedral co-ordination geometries for the metal ions. To prove the chelating nature of the ligand, and in particular the co-ordination of the amine nitrogen, the X-ray structure of one representative example was undertaken. Crystals of [Ni(bdmpae)(NO3)2] are of space group P21/c, with a= 8.511(3), b= 14.103(3), c= 15.865(8)Å, β= 92.75(3)°, and Z= 4. Standard least-squares refinements resulted in R= 0.041 (R′= 0.059). The nickel atom has a NiN3O3(mer) chromophore in a distorted octahedral geometry. One nitrate group is monodentate [Ni–O 2.052(5)Å], whereas the other is bidentate [Ni–O 2.157(5) and 2.145(5)Å]. Ni–N distances are 2.061 (5) and 2.034(5)Å for the pyrazole nitrogens and 2.128(5)Å for the amine nitrogen.

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