Structure of copper(II) complexes grown from ionic liquids - 1-ethyl-3-methyl-imidazolium acetate or chloride

Abstract

Crystals of four new copper(II) complexes have been grown from copper(II) acetate/chloride-1-ethyl-3-methyl-imidazolium acetate/chloride-water systems and characterized by X-ray analysis. The first complex, bis-(1-ethyl-3-methyl-imidazolium) tetra-μ-acetato-bis[chloridocuprate(II)], [Emim]₂[Cu₂(C₂H₃O₂)₄Cl₂] (1) (Emim is 1-ethyl-3-methyl-imidazolium, C₆H₁₁N₂), contains [Cu₂(C₂H₃O₂)₄Cl₂]^2- coordination anions with a paddle-wheel structure and ionic liquid cations. Two of the synthesized complexes are one-dimensional polymers, namely catena-poly[1-ethyl-3-methyl-imidazolium [[tetra-μ-acetato-dicuprate(II)]-μ-chlorido] monohydrate], {[Emim][Cu₂(C₂H₃O₂)₄Cl]·H₂O} _n (2), and catena-poly[1-ethyl-3-methyl-imidazolium [[tetra-μ-acetato-dicuprate(II)]-μ-acetato]], {[Emim][Cu₂(C₂H₃O₂)₅]} _n (3). In these compounds, the Cu₂(C₂H₃O₂)₄ units with a paddle-wheel structure are connected to each other through chloride (in 2) or acetate (in 3) anions to form parallel chains, between which cations of ionic liquid are situated. The last compound, bis-(1-ethyl-3-methyl-imidazolium) tetra-μ-acetato-bis[aquacopper(II)] tetra-μ-acetato-bis[acetatocuprate(II)] dihydrate, [Emim]₂[Cu₂(C₂H₃O₂)₄(H₂O)₂][Cu₂(C₂H₃O₂)₆]·2H₂O (4), contains two different binuclear coordination units (neutral and anionic), connected through hydrogen bonds between water mol-ecules and acetate ions.

Keywords: copper(II) complexes; crystal structure; ionic liquids; paddle-wheel.