The preparation of zinc(II) and cadmium(II) complexes of the pentadentate N 3S 2 ligand formed from 2,6-diacetylpyridine and S-benzyldithiocarbazate (H 2SNNNS) and the X-ray crystal structure of the novel dimeric [Zn 2(SNNNS) 2] complex

Abstract

The pentadentate chelating agent, 2,6-diacetylpyridinebis( S-benzyldithiocarbazate) (H 2SNNNS) reacts with zinc(II) and cadmium(II) ions forming stable complexes of empirical formula, [M(SNNNS)] (M=Zn 2+, Cd 2+; SNNNS 2=doubly deprotonated anionic form of the Schiff base). These complexes have been characterized by a variety of physico-chemical techniques. IR and 1H NMR spectral evidence indicate that the Schiff base coordinates to the zinc(II) and cadmium(II) ions via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the mercaptide sulfur atoms. The crystal and molecular structure of the zinc(II) complex has been determined by X-ray diffraction. The complex is a dimer in which the pyridine nitrogen atom,the azomethine nitrogen atom and the thiolate sulfur atom from one ligand coordinate to one of the zinc(II) ions whereas the azomethine and thiolate sulfur atoms from another ligand complete pentacoordination around the zinc(II) ion, the ligands being coordinated in their deprotonated forms. The coordination geometry about each zinc(II) can be considered as intermediate between a square-pyramid and trigonal-bipyramid. The cadmium(II) complex is also assigned with a dimeric structure.