Croatica Chemica Acta, Vol. 78 No. 4, 2005.
Original scientific paper
Estimation of Stability Constants of Copper(II) and Nickel(II) Chelates with 1,2-Diaminoethanes by the Overlapping Spheres Method
Ante Miličević
Nenad Raos
Abstract
The method of overlapping spheres (OS) was applied to the estimation of stability constants (log K1) of copper(II) and nickel(II) mono-complexes with 1,2-diaminoethane and its N-alkylated, N,N-dialkylated, and C-substituted derivatives. The central sphere, with radius 3 or 4 Å, was situated at the central atom, or in the equatorial (N1 or N2) or apical position (X1 or X2). The overlapping volumes of the central sphere and the van der Waals spheres of the surrounding atoms were calculated, and correlated with the stability constants measured at two temperatures, 0 and 25 °C. The regression analysis included the training set consisting of 14 ligands, subsequently divided into three subsets (classes), consisting of 5, 5, and 4 ligands. The general multivariate model including all the experimental data, i.e., log K1 for CuII and NiII complexes measured at 0 and 25 °C (N = 56), was developed by introducing two indicator variables. Predictive power of the best models was tested on stability constants of five copper(II) diamine chelates with highly variable structures, yielding the reproduction of experimental data with an error of 0.02–0.75 (rms = 0.34) log K units.
Keywords
coordination compounds; molecular volumes; indicator variable; CROMRsel procedure
Hrčak ID:
2540
URI
Publication date:
20.12.2005.
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