Studies with dithizone analogues-II Preparation and characterization of 2,2'-dichlorodithizone and the investigation of its reactions with some metal ions

1,5-Di-(2-chlorophenyl)-3-mercaptoformazan (2,2'-dichlorodithizone) has been synthesized and characterized. Its acid dissociation constant and its partition coefficient between carbon tetrachloride and water have been determined. The introduction of chlorine atoms into the ortho positions of the phenyl nuclei of dithizone was found to affect the visible electronic spectra of the reagent and its metal complexes. The ranges of pH for complete extraction, and the extraction constants, for the Hg(II), Cu(II), Zn(II), Cd(II), and Pb(II) complexes have been determined. The stability constants of the Cu(II) and Zn(II) complexes were also determined. Discrepancies between the present extensive data and the corresponding earlier data have been attributed to use of impure materials and/or inaccuracy of measurements in the earlier work.