Acetylene as a Bridging π-Ligand: Synthesis and Crystal Structure of NH4[Cu8Cl9(C2H2)4] • 2/5{[Cu(H2O)2]+[CuCl2]- • H2O}

The complex NH(4)[Cu(8)Cl(9)(C(2)H(2))(4)] center dot 2/5{[Cu(H(2)O)(2)](+)[CuCl(2)](-) center dot H(2)O} was synthesized by passing acetylene through an aqueous solution of CuCl that contained hydrochloric acid and minor amounts of NH(4)Cl. X-ray crystallography (DARCh automated diffractometer, lambda(Mo), R = 2.9%, 296 reflections with F >= 4 sigma(F)) showed that the compound crystallizes in the tetragonal crystal system with a = 11.624(4) angstrom, c = 9.543(3) angstrom, space group I4/mmm, Z = 2. The compound is structurally built of isolated [Cu(8)Cl(9)(C(2)H(2))(4)](-) units, 4/mmm symmetry, which form, together with NH(4)(+) cations, chains {NH(4)[Cu(8)Cl(9)(C(2)H(2))(4)]}(n) of the host complex running along the fourfold axis. Acetylene molecules are simultaneously involved in back-donation with two copper atoms; the C C bond length is equal to 1.233(9) angstrom. In addition, a guest complex ([Cu(H(2)O)(2)](+)[CuCl(2)](-) center dot H(2)O) is present on the (4) over bar axis; it forms a linear chain of copper, chlorine, and oxygen atoms, with incomplete occupation of the corresponding positions.