Coordination chemistry of [methyl-3-(4-benzyloxyphenyl)methylene]dithiocarbazate with divalent metal ions: crystal structures of the N,S Schiff base and of its bis-chelated nickel(II) complex

The condensation of 4-benzyloxybenzaldehyde with S-methyldithiocarbazate (SMDTC) yielded the Schiff base methyl-3-[(4-benzyloxyphenyl)methylene] dithiocarbazate (HL) that, upon reaction with different metal ions, afforded bis-chelated complexes, ML 2 [where M=Ni(II), Cu(II), Zn(II), Cd(II) or Pd(II)]. The ligand and all the metal complexes were characterized by physico-chemical and spectroscopic methods. The Schiff base and its bis-chelated Ni(II) complex were characterized also by single crystal X-ray analyses. The crystallographic results show that the Schiff base exists in thione tautomeric form with the dithiocarbazate fragment adopting an EE configuration with respect to the C=N bond of the group. In the NiL 2 complex, the metal is chelated by two mononegatively charged Schiff bases coordinating via the β -nitrogen and thiolate sulfur anion, generated in situ during the complexation process, and adopts a distorted square planar geometry.