Zum Einfluß der Zusammensetzung gemischter Lösungsmittel auf die Stabilitäts- und Bildungskonstanten von Kupfer(II)- und Nickel(II)-Komplexen substituierter 1,2-Dioxime

Influence of the Composition of Mixed Solvents on the Stability and Formation Constants of Copper (II) and Nickel(II) Complexes of Substituted 1,2-Dioximes The stability constants ^cK₁, ^cK₂, and _cβ₂ of the complexes which are formed in the systems M²⁺/DH₂, M²⁺/Ac? DH₂, and M²⁺/Et, Me\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus $\end{document}? DH₂ (M²⁺ ? Cu²⁺, Ni²⁺; DH₂, Ac? DH₂, Et₂Me\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus $\end{document}? DH₂ = 1,2-dioximes) are determined in water and in water-dioxane mixtures (25, 50 and 75 per cent). Because of the stabilisation of the l,2-complexes by intramolecular hydrogen bonds ^cK₂, is always higher than ^cK₁. On account of the decrease of the dielectricity constant the constants ^cK₁, ^cK₂, and ^cβ₂, rise with increasing contents of dioxane in the mixtures. The influence of the dielectricity constant may be eliminated by considering the formation constants ^cK_1(B), ^cK_2(B), and ^cβ_2(B). The individual formation constants ^cK_1(B) of the 1,l-complexes investigated are independent of the composition of the solvent, but among the overall formation constants ^cβ_2(B) this comes true only for the complexes Ni(Ac? DH)₂, Ni(Et₂Me\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus $\end{document}? DH)₂, and Cu(Et₂Me\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ \oplus $\end{document}? DH)₂. With Cu(DH₂) and Cu(Ac? DH)₂ a linear relation between log ^cβ_2(B) and the molar fraction of water is stated. This effect is attributed to a specific solvatation of the chelates Cu(DH)₂ and Cu(Ac? DH)₂ by water.