Crystal structure and spectroscopic studies on metal complexes containing ns donor ligands derived from S-benzyldithiocarbazate and p-dimethylaminobenzaldehyde

Abstract

A series of neutral bis-ligand Cu II, Ni II, Pd II and Pt II chelates with Schiff base ligands derived from S-benzyldithiocarbazate and p-dimethylaminobenzaldehyde were prepared and characterized. The Schiff base acts as a single, negatively charged bidentate ligand forming stable neutral metal complexes. Magnetic and spectroscopic data suggest a square-planar structure for the Ni II, Pd II and Pt II chelates. Also, ESR spectral and variable-temperature magnetic suspectibility data support the square-planar structure of Cu II chelate. Cyclic voltammograms show that the coordination ability of the metal is the main factor influencing the redox potential of the Schiff base ligand in the complexes. Single cyrstal X-ray diffraction analysis of the nickel(II) chelate established that the Schiff base has lost a proton from its tautometric thiol form and coordinated to Ni II via the mercapto sulphur and β-nitrogen. The geometry around Ni II is square-planar with two equivalent Ni N and Ni S bonds; the two dimethylaminophenyl rings and the coordinated plane are almost in one plane forming an electronic delocalization system.