The effect of hydrogen bonding on the chlorocuprate(II) geometry. A compound containing an unusual copper(II)/chlorine ratio of 1:6. Crystal and molecular structure of bis(Nbenzylpiperaziniumchloride) tetrachloro cuprate(II).

A compound of the type (NBzpipzH2)2CuCl6 (NBzpipzH2)2 = N-benzylpiperazinium dication) was prepared and characterized by means of X-ray, electronic, differential scanning calorimetric and magnetic measurements. Crystal of the compound are monoclinic, space group Pc with a = 21.954(2) Å, b = 7.0889(5) Å, c = 9.1391(9) Å, β = 97.054(8)°, and Z = 2. Intensities were obtained from 0–20 scan with a Philips PW 1100 automatic four-circle diffractometer using graphite-monochromated Mo Kα radiation. The structure was solved by conventional heavy-atom methods, and least-squares refinement of structural parameters led to a conventional R factor of 0.049 for 1508 reflection having I > 3σ(I). The crystal consists of a CuCl2−4 anion, two lattice Cl− ions, and two (NBzpipzH2)2+ cations. The CuCl2−4 ion shows a slight tetrahedral distortion superimposed to the basic square-planar geometry, but may be also regarded as an example of an extremely flattened tetrahedron. The strong hydrogen bonds formed by the N-bonded H atoms of the cations, which bridge the CuCl2−4 anions and link the Cl− ions, were considered responsible for the unusual geometry of the CuCl2−4 chromophore. The electronic spectra are discussed and assigned on the basis of the known crystal structure.