A kinetic study of the formation of some unchelated and chelated beryllium(II) complexes in aqueous solutions

Abstract

Beryllium(II) ions form unchelated [Be(H L)]⁺ and chelated [BeL] complexes with the dicarboxylate anions (L^2–) oxalate, malonate, succinate, and maleate. From kinetic experiments, rate and equilibrium constants have been obtained for the formation of both types of complex. Ring closure is the rate-determining step of the overall reactions. For beryllium and hydroxycarboxylates only the formation of unchelated complexes is observed and no evidence is found for the existence of chelated complexes. The rate constant for the formation of the unchelated complexes is independent of the anion, k₁= 200 ± 50 s^–1, and agrees with the corresponding value for beryllium sulphate. The rate constant for the formation of the chelated complexes and the equilibrium constants depend on the nature of the ligand.