Synthesis and structural features of copper(I) chloride and bromide complexes with the N,N,N′,N′-tetraallylpiperasinium cation (L2+) of compositions L2+ [CuCl2]2- and L2+[CuBr3]2-

Crystals of the pi-complex [C4H8N2(C3H5)(4)](2+)[CuCl2](2)(-) (I) were prepared by ac electrochemical synthesis from copper and N,N,N',N'-tetraallylpiperasinium chlorides in alcohol solution. Similar synthesis with the use of the metal and N,N,N',N'-tetraallylpiperasinium bromides yielded the complex [C4H8N2(C3H5)(4)](2+)[CuBr3](2-) (II). Structures I and II were studied by X-ray diffraction (DARCh automated single-crystal diffractometer, MoKalpha radiation). Crystals of I are triclinic, space group P(1) over bar, a = 8.650(3) Angstrom, b = 7.572(2) Angstrom, c = 8.095(3) Angstrom, alpha = 100.45(2)degrees, beta = 83.91(2)degrees, gamma = 99.89(2)degrees, V = 512.1(6) Angstrom(3), Z = 1. Crystals of II are orthorhombic, space group Pn2(1)a, a = 17.673(3) Angstrom, b = 14.369(6) Angstrom, c = 8.244(2) Angstrom, V = 2093(2) Angstrom(3), Z = 4. In structure 1, the potentially tetradentate N,N,N',N'-tetraallylpiperasinium cation uses two centrosymmetric allyl groups for bonding with copper atoms, whose environment is completed to the trigonal-planar coordination with the chlorine atoms. The [C4H8N2(C3H5)(4)](2+)[CuCl2](2)(-) groups are joined into a three-dimensional framework by weak hydrogen bonds. The inorganic fragment CuCl is partially disordered, which appears as "splitting" of the positions of the copper atom and one of the chlorine atom. In compound II, the inorganic fragment occurs as an unusual trigonal-planar CuBr32- anion; the N,N,N,N'-tetraallylpiperasinium cation is not involved in metal coordination.