Unique Isle Anion [Cu6Cl10]4- in π-Complex of Cu(I) Chloride with 1-(2-Pyridyl)-4-allyl-piperazinium. Synthesis and crystal structure of [(C5H4NH)NC4H8NH(C3H5]2+[Cu3Cl5]2-

Single crystals of [(C₅H₄NH)NC₄H₈NH(C₃H₅)]²⁺[Cu₃Cl₅]^2? are obtained by ac synthesis in ethanol from 1-(2-pyridyl)-4-allyl-piperazinium and Cu(II) dichlorides and their structure is studied by X-ray diffraction analysis (space group P-1, a = 7.246(7) Å, b = 8.54(1) Å, c = 16.41(1) Å, α = 70.76(8)°, β = 77.24(8)°, λ = 80.42(9)°, V = 30(4) ų, Z = 2, R(F) = 0.0686. In the structure of this π-complex, the Cu and Cl atoms form unusual centrosymmetrical Cu₆Cl₁₀ fragments, each fragment being bonded to two 1-(2-pyridyl)-4-allyl-piper-azinium cations via π-interaction Cu-(C=C). A three-dimensional structure is formed by means of N-H…Cl hydrogen bonds. The trigonal-pyramidal surrounding of the Cu(1) atom includes three Cl atoms and the C=C bond, while the tetrahedral surrounding of Cu(2) and the trigonal surrounding of Cu(3) involve the Cl atoms only.