Unambiguous cis-coordination of mono- and bi-dentate Lewis bases to Ni(SN) 2 Schiff-base complexes derived from S-alkyl dithiocarbazate

Abstract

The bidentate Schiff-base ligand, HL 1, prepared by condensation of equivalent molar amount of o-nitrobenzaldehyde with S-benzyl dithiocarbazate, yielded the neutral square-planar complex, NiL 1 2 ( 1) in the presence of Ni(OAc) 2·4H 2O. Addition of pyridine to ( 1) and phenanthroline (phen) to NiL ( 3) afforded the adducts NiL 1 2(py) 2·1.5H 2O ( 2) and NiL(phen) ( 4), respectively, where H 2L is a known quadridentate (NS) 2 ligand. Single crystal X-ray analysis of ( 2) and ( 4) showed that the pyridine rings and phen occupy cis-positions in the octahedral adducts. In both cases, one N–Ni bond in the parent Ni(NS) 2 complexes is severely perturbed, thus facilitating cis-addition of the Lewis bases. The present results together with those reported previously show that cis-addition is preferred in the addition reaction of Ni(NS) 2 Schiff-base complexes derived from S-alkyl dithiocarbazate. Addition of pyridine and 2,2′-bipyridine to NiL ( 3) is also discussed.