Multidentate behaviour of 2-formylcyclohexanone schiff bases in the Co(II), Ni(II), Cu(II) and Zn(II) complexes

Abstract

Metal(II) chelates of schiff bases derived from the condensation of 2-formylcyclohexanone with <i>o</i>-aminophenol (FCAP), <i>o</i>-arninothiophenol (FCAT) or <i>o</i>-aminobenzoic acid (FCAB) have been orepared and characterized. The complexes are of the type M(ONX)nB for M = CU(II) and Zn(II), and M(NX)₂nB for M =Co(ll) and Ni(II) [X = phenolic oxygen, sulphur or carboxylic oxygen; B =H₂O. Py; n =0, 1 and 2]. Conductivity data indicate non-ionic nature of the complexes. IR and PMR data show that while the free ligands exist in the ketarnine form, in the complexes they exist in the enimine form. All the schiff bases behave as dibasic tridentate ligands in the CU(II) and Zn(II) complexes and monobasic bidentate ligands in Ni(II) and Co(II) complexes. The subnormal magnetic moments of Cu(II) complexes are ascribed to antiferromagnetic interaction arising from dimerisation: Pyridine cleaves the dimers to afford square-planar monomers with pyridine occupying the fourth coordination site. Ni(II) and Co(II) complexes of FCAP and FCAT schiff bases are low-spin with squareplanar structure while the corresponding FCAB schiff base complexes are high-spin with octahedral geometry.