Polynuclear complex formation between Cd(II) and 3-(dimethylamino)-l-propanethiol has been studied by means of 382 emf measurements with a glass electrode in 7 separate titrations at 25 °C in 3 M NaC104 medium (10% (v/v) CH3OH). Conclusions drawn from the graphical methods based on the “core + links” hypothesis and on the “extended variation method” agree with the results obtained from the numerical treatment. Experimental data at 3 < pH < 11 can be explained by assuming that the following complexes predominate in a wide pH range: [Cd(HA)4]2+, [Cd3(HA)6]6+, [Cd3(HA)8]6+, [Cd4(HA)9]8+, and [Cd4-(Ha)I0]8+, HA being the uncharged ligand. The deprotonation of these species gives rise to several mononuclear and polynuclear ternary complexes CdpAqHr, (r < q), A denoting the completely deprotonated ligand. Experimental data suggest that chelate formation does not take place. The stoichiometries of the [Cdp(HA)q]2p+ soluble species found in several Cd(II)-aliphatic γ-mercapto amine systems are compared, and their possible geometry is analyzed. The influence of the flexibility of the hydrocarbon chain and of the degree of substitution on the amine function as factors affecting the chelating ability of γ-mercapto amines is discussed. © 1989, American Chemical Society. All rights reserved.
|Publication status||Published - 1 Jan 1989|