Copper(I) halide complexes with N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L2+). Synthesis and crystal structures of the complexes [L0.5CuCl2], [L0.5CuCl0.72Br1.28], and [L0.5CuBr2

Abstract

The Eschweiler-Clarke reaction of ethylenediamine with formaldehyde and formic acid yielded N,N,N′,N′-tetramethylethylenediamine, which was alkylated with allyl chloride or allyl bromide to give the corresponding N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L2+) dihalides. In methanolic solutions of copper(II) halide and an appropriate ligand, ac electrochemical synthesis with copper wire electrodes afforded single crystals of Cu(I) complexes with L2+: [L0.5CuCl2] (I), [L0.5CuCl0.72Br1.28] (II), and [L0.5CuBr2] (III). The crystal structures of complexes I–III were determined by X-ray diffraction study. The isostructural crystals of I and II are monoclinic, space group P21/n, Z = 4. For I: a = 7.632(4) A, b = 11.318(5) A, c = 10.635(5) A, β = 98.551(7)°, V = 908.4(7) A3. For II: a = 7.7415(7) A, b = 11.4652(9) A, c = 10.7267(10) A, β = 98.351(4)°, V = 942.0(2) A3. The organic cation L2+ acts as a bridge linking a pair of separate cuprous halide fragments Cu2X4. Although being isostoichiometric with I and II, complex III has a different structure. The crystals of III are monoclinic, space group P21/c, a = 6.519(2) A, b = 9.060(3) A, c = 16.284(6) A, β = 97.219(4)°, V = 954.2(6) A3, Z = 4. In structure III, the inorganic fragment forms infinite polymer chains (CuBr2−)n. The organic and inorganic parts are held together only by electrostatic interactions. Structures I–III are stabilized by hydrogen bonds (C)H…X (2.6–2.9 A).