Extraction Equilibria of Nickel(II) with 3-Mercapto-1,5-Diarylformazans in the Presence of 2,2′-Bipyridyl or 1,10-Phenanthroline

Abstract

Abstract The equilibria associated with nickel(II) extraction from aqueous solutions with 3-mercapto-1,5-diarylformazans (dithizone analogues, RPh-N=N-C(=S)NH-NH-PhR; H2R2Dz) in the presence of 2,2′-bipyridyl or 1,10-phenanthroline (L) has been investigated. The reactions between H2R2Dz and [NiL]2+, [NiL2]2+ and [NiL3]2+ were also studied and found to give identical ternary nickel(II) complexes, Ni(HR2Dz)2L. The absorption spectral characteristics of ternary complex species extracted from perchlorate solutions were found to be different from those of the corresponding ternary complex species extracted from chloride, acetate, phosphate or sulfate solutions. The reaction equilibria between binary nickel(II) 3-mercapto-1,5-diarylformazan complexes, Ni(HR2Dz)2 and 2,2′-bipyridyl or 1,10-phenanthroline were also investigated and the formation constants of the ternary complex species were calculated. The effect of substituents R, on the extraction or formation constants of the ternary complexes are discussed and correlated with Hammett′s σ+ values.