Reactions of 1,1,1-tris(aminomethyl)alkanes with nickel(II), copper(II), zinc(II), and hydrogen ions. A calorimetric and spectrophotometric investigation

Abstract

The enthalpy changes for the reactions of Ni²⁺, Cu²⁺, Zn²⁺, and H⁺ with CH₃C(CH₂NH₂)₃ and CH₃CH₂C(CH₂NH₂)₃ at 298 K in aqueous solution (0.5 mol dm^–3 K[NO₃]) have been determined using continuous calorimetric titrations. The LKB–8700 calorimeter has been suitably modified for this purpose. A FORTRAN IV computer program has been employed to obtain the heats of formation of the complex species from the experimental data. By combination of the values of the enthalpy changes with the corresponding free-energy changes, reported elsewhere, values of the entropy of reactions have been calculated. Inspection of these thermodynamic quantities allows conclusions to be made about the co-ordinating properties of the two ligands. The visible spectra of the copper(II) complexes have been determined in order to get additional information about their structures.