Isomerism in copper(II) chloride complexes of bis(2-pyridylmethyl)amine and N-substituted derivatives: Synthesis and X-ray structural characterisation

Abstract

Copper(II) chloride complexes of tridentate N-alkylated bis(2-pyridylmethyl)amine ligands (R-bpa) form coordination oligomers with either terminal or bridging chloride. Two structural types are identified by X-ray diffraction: a mono μ-chloro bridged species and a di-μ-chloro bridged species, both containing five-coordinate copper(II). In each case, the τ parameter indicates only small deviations from regular square-pyramidal coordination geometry. The product structure is dependent on the presence or absence of non-coordinating anions. In the presence of ClO 4 - or PF 6 - , cationic dinuclear complexes are formed, driven by the formation of an ionic lattice. In the absence of non-coordinating anions, neutral mononuclear [CuCl 2(R-bpa)] complexes are formed. Chloride concentration in methanol solution exerts less influence on the reaction outcome, despite differing chloride stoichiometries in the isolated products. In the presence of the coordinating acetate anion, cationic products are formed in which the terminal chloride ligands are completely or partially substituted by acetate.