Single-crystal to single-crystal transformations in discrete hydrated dimeric copper complexes

Abstract

The single crystals of discrete hydrated [(OAc)Cu(μ-hep)₂Cu(OAc)]·2H₂O (1·2H₂O) and [(OAc)Cu(μ-hep)₂ Cu(OⁿPr)]·2H₂O (2·2H₂O) (the lattice H₂O molecules exist as a tetrameric water cluster, hep-H = 2-(2-hydroxyethyl)pyridine), OAc⁻ = acetate and OⁿPr⁻ = n-propionate) undergo single-crystal to single-crystal (SCSC) transformations to the dehydrated 1 and 2, respectively, under the influence of heat. The reverse SCSC processes of 1/2→1·2H₂O/2·2H₂O involving the regeneration of the lattice water tetramers take place on exposure of 1/2 to water vapour. However, the blue single crystal of discrete hydrated [(OⁿPr)Cu(μ-hep)₂Cu(OⁿPr)]·2H₂O (3·2H₂O), incorporating the two bulkier OⁿPr⁻ terminal bidentate ligands, irreversibly converts to the green single crystal of a unique discrete tetrameric [Cu₄(μ₃hep)₂(μ-hep)₂(μ-OⁿPr)₂(OⁿPr)₂] (4) with double open cubane core either by heating or by a simple vapour diffusion technique via the breaking and forming of multiple covalent bonds.