A polymeric cationic copper(I) complex involving a quadruply bridging, zwitterionic thiolate ligand: {[Cu8Cl6(SCH2CH2NH3)6]Cl2}n

Abstract

Solutions obtained by dissolving copper(I) chloride in an excess of aqueous cysteamine hydrochloride (HSCH₂CH₂NH₃Cl) deposited a white solid, for which X-ray diffraction revealed a unit cell of composition Cu₈Cl₈(SCH₂CH₂NH₃)₆. The material has a complex polymeric columnar structure containing three-co-ordinate copper(I) atoms linked in various ways to the zwitterionic ligand ^–SCH₂CH₂NH₃⁺; six chloride ions are bound to copper and two are ionic, so that the polymer chain is positively charged. The thiolate sulfur atoms bridge either three or four metal atoms, making the sulfur four- or five-co-ordinate. This is only the second reported example of the latter type of co-ordination, which is electron deficient. pH Measurements confirmed the release of one H⁺ for each CuCl dissolved, and NMR data showed that the thiol undergoes copper-catalysed aerial oxidation in the time between making the solution and the appearance of the polymeric product. The oxidation reduces the copper∶ligand ratio to levels allowing the formation of polymeric products.