Benzoyl-beta-alaninato nickel(II) complexes. The amino effect on the amino acid coordination around the nickel ion.

A compound of the type Ni(Bz-β-ala)2·2H2O (Bz-β-ala=benzoyl-β-alaninate anion) and its amine adducts of the type Ni(Bz-β-ala)2Bn·xH2O (n=1; B=piperazine (pipz), 1,10-phenanthroline (o-phen) and x=2; n=1, B=2,2′-bipyridine (2,2′-bpy) and 4,4′-bipyridine (4,4′-bpy) and x=4; n=2, B=N-methylpiperazine (CH3-pipz), morpholine (morph), pyridine (py), 3-methylpyridine (3-pic) and 4-methylpyridine (4-pic) and x=2; n=3, B=en, and x=0) were prepared. Each complex was characterized by elemental analysis, solid spectroscopy and magnetic moment. All the complexes are six-coordinated and the presence of NiO6 and NiN6 chromophores for Ni(Bz-β-ala)2·2H2O and Ni(en)3(Bz-β-ala)2 complexes respectively and of NiO4N2 chromophores for the amine adducts is suggested. In all the complexes the amino acid appears to act as a bidentate ligand toward the carboxyl group. A ligand field strength in the aromatic heterocyclic amine adducts was found greater than in the aliphatic heterocyclic amine adducts. The amine adducts complexes appear to dissociate in solution with a change of the donor site, without changing in the stereochemistry, around the nickel ion.