The crystal structure and ESR studies of diamminecopper(II) tetracyanoniccolate(II) dibenzene clathrate: Cu(NH 3) 2Ni(CN) 4.2C 6H 6

Abstract

The crystal structure of Cu(NH 3) 2Ni(CN) 4.2C 6H 6 was determined by three-dimensional X-ray methods. The crystal is tetragonal with the dimensions of a = 7.345 A and c = 16.519 A, and the space group is P4/mcc ( Z = 2). Reflection data were collected with an automatic four circle diffractometer and monochromatized Mo Kα radiation. The structure was solved by the heavy-method and was refined by the block-diagonal least-squares method for 690 independent reflections to a final R-index of 0.068. The copper ions and the nickel ions are linked crosswise with the cyanide anions to form a polymeric two-dimensional metal complex network, and the benzene molecules are trapped among the layers of the networks. This host lattice structure is similar to those of the other Hoffmann-type clathrates, Ni(NH 3) 2Ni(CN) 4. 2C 6H 6 and Cd(NH 3) 2Ni(CN) 4. 2C 6H 6, but the c-axis of the cell is doubled due to different orientation of the benzene molecules in alternate guest layers. The copper(II) ion takes a compressed tetragonal coordination with the four nitrogen atoms of the cyanide anions in the (001) plane (the Cu-N distance, 2.20 A) and with the two nitrogen atoms of the ammonia molecules of the [001] axis at the compressed apical positions (the Cu-N distance, 2.05 A). The ESR spectra of the magnetically dilute single crystal of (Cd, Cu)(NH 3) 2Ni(CN) 4. 2C 6H 6 can be interpreted in terms of A 1g symmetry of the electronic ground state of the copper(II) ion in the compressed tetragonal environment which was previously concluded from the spectra of the polycrystalline samples.