Polymeric thiolate complexes in solution. Stability constants of the zinc(II) complexes of 1-methyl-4-mercaptopiperidine

Abstract

The equilibrium reaction between Zn^II and 1-methyl-4-mercaptopiperidine has been studied by e.m.f. measurements with a glass electrode at 25 °C in a 3 mol dm^–3(sodium) perchlorate medium [+10%(v/v) CH₃OH]. Conclusions drawn from graphical methods based on the ‘core + links’ hypothesis are in agreement with the results obtained from the numerical treatment. The e.m.f. data obtained in the range 4 < –log[H⁺] < 9 can be explained by assuming the existence of the following species: [Zn₃(HA)₆]⁶⁺(log ψ_{3, 6}= 39.71 ± 0.01), [Zn₅(HA)₁₂]¹⁰⁺(log ψ_5,12= 79.87 ± 0.01), and [Zn₂(HA)₆]⁴⁺(log ψ_2,6= 35.26 ± 0.02) where HA is the uncharged ligand. A mechanism for the formation of these species and their possible geometries are suggested.