Synthesis and spectral studies of nickel(II) complexes derived from disalicylaldehyde oxaloyldihydrazone

Abstract

The mononuclear nickel(II) complex [Ni(H2slox)(H2O)3] (1) and polymeric dinuclear complexes [Ni2(slox)(A4)] {A = H2O (2), py (3), 2-pic (4), 3-pic (5) and 4-pic (6)} and the discrete binuclear complexes [Ni2(slox)(NN)3] {NN = bpy (7) and phen (8)} have been synthesized from disalicylaldehyde oxaloyldihydrazone (H4slox) in methanol. All of the complexes are nonelectrolytes. Complexes 1, 7, and 8 are paramagnetic while binuclear 2–6 possess anomalously low μ eff value, indicating considerable metal–metal interaction. Discrete binuclear 7 and 8 have no interaction between the two nickel(II) ions. The anomalously low magnetic moment values in 2–6 are explained as metal–metal interaction via phenoxide bridge. Such metal–metal interactions are less in 7 and 8 due to coordination of bipyridine and phenanthroline molecules which do not allow phenoxide bridging. The dihydrazone coordinates to the metal center as a dibasic tridentate ligand in keto-enol form in staggered configuration in 1, while in the remaining complexes the dihydrazone is tetrabasic hexadentate in enol form in anticis configuration. The metal center has a tetragonally distorted octahedral stereochemistry.