Nickel(II) complexes with N2OS and N2S2 co-ordination spheres: reduction and spectroscopic study of the corresponding Ni(I) complexes

Nickel(II) complexes with Schiff-bases obtained by condensation of 1,3-prop anediamine with salicylaldehyde and thiosalicylaldehyde, which present a N2 OS or N2S2 co-ordination sphere, were synthesized and studied. The molecula r and crystal structure of the asymmetric complex [2-({3-[(3,5-dichloro-2-h ydroxyphenyl)methyleneamino]propyl}iminomethylene)benzenethiolato-O,N,N',S] nickel(II) [Ni(t-salCl(2)salpd)] has been determined by X-ray crystallograp hy and shows a tetrahedrally distorted square-planar co-ordination geometry for the nickel center. The complexes were characterized by spectroscopic a nd electrochemical techniques and the results were used to assess the influ ence of the donor-atoms on their chemical properties. The results obtained show that the compounds may be reduced, either chemically or electrochemica lly, to Ni(I) complexes. Reduction potentials were found to be strongly dep endent on the tetrahedral distortion of the Ni(II) complexes. EPR parameter s for Ni(I) complexes, although not very sensitive to ligand substituents, show a regular dependence on the co-ordination set and the tetrahedral dist ortion of the complexes.