Calculations of the intrinsic constants of the complexation between Cu(II) and halide ions in solution

Abstract

Experimental curves of spectrophotometric titration for systems containing mononuclear homoleptic complexes were interpreted in an alternative way involving calculation of the intrinsic constants of binding of the ligand by a central ion with fixed coordination sites. This matrix approach allows one to reduce the number of variables in least-squares optimization of titration curves, describing the formation of complexes [MXn] (n = 1–4) via three independent variables (\( \bar K \), ωcis and ωtrans) for a square planar geometry and via two variables (\( \bar K \) and ω) for a tetrahedral geometry. Differences in the mutual cis-and trans-influences of coordinated ligands were quantitatively estimated for labile complexes in solution. The method proposed was used to calculate the intrinsic constants of complexation between Cu2+ and the chloride ion in methanol from spectrophotometric titration data.