Crystalline Phase Transitions and Water-Soluble Complexes of Copper(I) 2-Hydroxyethanethiolate

Abstract

The coordination polymer copper(I) 2-hydroxyethanethiolate, (CuSCH₂CH₂OH)_n, though insoluble in all common solvents, dissolved readily in basic aqueous solutions of the thiolate anion (HOCH₂CH₂S^–) of 2-mercaptoethanol to form a single species: the tetranuclear cluster [Cu₄(μ-SCH₂CH₂OH)₆]^2–. From this solution were grown X-ray quality single crystals of copper(I) 2-hydroxyethanethiolate. This compound underwent a hitherto unknown crystal phase transition at ca. 6 °C, from point group P2₁2₁2₁ to Pna2₁, with noticeable changes in the geometry of the Cu-S layer and in the orientation of the alkylthiolate side chains. When the bulky base tetrabutylammonium hydroxide was employed in the aqueous thiolate solution used to dissolve (CuSCH₂CH₂OH)_n, the water-soluble polynuclear copper(I) complex bis(tetrabutylammonium) hexakis(µ-2-hydroxyethanethiolato) tetracuprate(I), [(C₄H₉)₄N]₂[Cu₄(μ-SCH₂CH₂OH)₆], could be isolated as X-ray quality crystals. Structural characterization of this complex revealed a tetrahedral arrangement of copper(I) centers with thiolates bridging the edges of the tetrahedra. On standing, this complex degraded to a larger polynuclear Cu(I) sulfide cluster.