Crystal structures of Cd(H2O)(2)Cu(CN3).2H(2)O, K[Cd(H2O)(2)Cu-2(CN)(5)].2H(2)O and K-2[Cd(H2O)Cu-4(CN)(8)].1.5H(2)O. Structures of multi-dimensional frameworks formed with cadmium(II), copper(I), and bridging cyano groups

In an attempt to form new multi-dimensional structures of cyano complexes including cadmium(II) and copper(I), four new complexes were obtained successively from an aqueous solution at intervals of from a few days to a few months. The complex 1 obtained first was unstable in the atmosphere. The crystal structures of the other complexes (2-4) obtained from second to fourth were determined by single crystal X-ray structure determinations. Their crystal data are as follows: 2 Cd(H2O)(2) Cu(CN)(3) . 2H(2)O, monoclinic, C2/m, a = 14.038(1), b = 9.944(1), c = 7.738(1) Angstrom, beta = 116.019(7)degrees, 2 = 4; 3 K[Cd(H2O)(2)Cu-2(CN)(5)]. 2H(2)O, triclinic, P (1) over bar, a = 17.429(9), b = 16.519(7), c = 10.085(5) Angstrom, alpha = 128.60(3), beta = 137.44(2), gamma = 45.82(2)degrees, Z = 4; 4 K-2[Cd(H2O)Cu-4(CN)(8)]. 1.5H(2)O, monoclinic, C2/c, a = 19.387(2), b = 16.056(3), c = 12.683(2) Angstrom, beta = 110.419(9)degrees, Z = 4. The main structural feature found in the complexes is that the whole framework consists of two networks, a Cd-Cu(I)-CN complex network that has an infinite network formed with bridging cyano groups between the metal atoms and a network formed with hydrogen bonding among water molecules. The second network is connected to Cd in the Cd-Cu(I)-CN complex network via a water ligand coordinated to Cd. In 2 a planar network of [CdCu(CN)(3)] complexes are stacked along the c axis and the second network links the stacked complexes. 3 has a stacked structure of [Cd(H2O)(2)Cu(CN)(5)](2-) in a bi-layered structure. The second network of 3, which includes K+ ions with an electrostatic interaction, spreads over the crystal, penetrating vacant spaces of the metal complex network. 4 has a double lattice structure with a pair of enantiomeric three-dimensional [Cd(H2O)Cu-4(CN)(8)](2-) complexes inter-penetrating each other. There are three structural factors for forming these framwork structures: (1) a non-planar coordination structure for Cd(II) that extends the planar structure of the Cu(I)-CN complex to a three-dimensional structure for the Cd-Cu(I)-CN complex; (2) a trigonal planar coordination structure for Cu(I) that generates vacant space in the metal complex network and makes possible hydrogen bonds to form the second network; (3) structural distortions of bridging cyano groups and a coordination structure of Cu(I) that cause variations of the metal complex network structure.