New π ligand N,N,N,N′,N′,N′-hexaallylethylenediaminium (L2+): Synthesis and crystal structures of LBr2 · 2H2O and its cuprocomplexes L[CuII(Br0.45Cl3.55)], L[Cu 4 I (Br4.55Cl1.45)], and L[Cu 4 I Br6]

The alkylation of ethylenediamine with allyl bromide in the presence of a fourfold (with respect to ethylenediamine) molar amount of NaHCO3 in acetone with an ethanol admixture (15: 1) affords LBr2 · 2H2O (I), where L2+ is the N,N,N,N′,N′,N′-hexaallylethylenediaminium cation. Single crystals of complexes L[CuII(Br0.45Cl3.55)] (II), L[Cu 4 I (Br4.55Cl1.45)] (III), and L[Cu 4 I Br6] (IV) are prepared by ac electrochemical synthesis from an ethanolic solution of LBr2 · 2H2O, CuCl2 · 2H2O (or CuBr2) at copper wire electrodes. The crystal structures of compounds I–IV are determined by X-ray diffraction analysis. The crystals of complex I are monoclinic: space group P21/n, a = 8.544(3), b = 10.404(3), c = 13.350(4) A, β = 97.29(3)°, V = 1177.2(6) A3, Z = 2. The bromine anions in compound I are bonded to the L2+ cations and water molecules through hydrogen contacts (E)H…Br (E = O, C) of 2.57(3)–2.86(3) A. The crystals of compounds II–IV are triclinic: space group P \( \bar 1 \). For II: a = 8.762(4), b = 9.163(4), c = 16.500(6) A, α = 95.62(4)°, β = 96.39(4)°, γ = 111.46(4)°, V = 1211.4(9) A3, Z = 2; for III: a = 9.074(4), b = 9.435(4), c = 9.829(5) A, α = 116.12(4)°, β = 104.14(4)°, γ = 100.22(4)°, V = 692.3(6) A3, Z = 1; for IV isostructural III: a = 9.084(4), b = 9.404(4), c = 9.869(4) A, α = 116.31(3)°, β = 104.00(3)°, γ = 100.37(3)°, V = 692.1(5) A3, Z = 1. Unlike the isolated tetrahedral CuX 4 2− anion in structure II, an original chain anion (Cu4X 6 2− ) n is observed in the structures of π complexes III and IV.