THE PREPARATION AND CHARACTERIZATION OF SOME NEW NICKEL(II), COPPER(II), ZINC(II) AND CADMIUM(II) COMPLEXES OF THE PYRROLE-2-CARBOXALDEHYDESCHIFF-BASES OF S-ALKYL ESTERS OF DITHIOCARBAZIC ACID

New complexes of general formulae [Ni(HL)2], [ML].H2O and [Cu(HL)X] (H 2L = pyrrole-2-aldehyde Schiff bases of S-methyl- and S-benzyldithioca rbazates; X = Cl or Br; M = Ni(II), Cu(II), Zn(II) or Cd(II)) were pre pared and characterized by a variety of physicochemical techniques. Th e Schiff bases coordinate as NS bidentate chelating agents in [Ni(HL)2 ] and [Cu(HL)X], and as tridentate NNS chelates in [ML] (M = Ni(II), C u(II), Zn(II) or Cd(II)). Both the [Ni(HL)2] and [NiL] complexes are d iamagnetic and square-planar. Based on magnetic and spectroscopic evid ence, thiolate sulphur-bridged dimeric square-planar structures are as signed to the [Cu(HL)X] and [ML] (M = Ni(II) or Cu(II)) complexes. The complexes ML (M = Zn(II) or Cd(II)) are polymeric and octahedral.