Syntheses and crystal structures of bis-(4-methyl-pyridine-κN)bis-(seleno-cyanato-κN)zinc(II) and catena-poly[[bis-(4-methyl-pyridine-κN)cadmium(II)]-di-μ-seleno-cyanato-κ2 N:Se;κ2 Se:N

Abstract

The reactions of Zn(NO3)2 .6H2O and Cd(NO3)2 .4H2O with KSeCN and 4-meth-yl-pyridine (C6H7N; 4-picoline) lead to the formation of crystals of bis-(4-methyl-pyridine-κN)bis-(seleno-cyanato-κN)zinc(II), [Cd(NCSe)2(C6H7N)2] (1), and catena-poly[[bis-(4-methyl-pyridine-κN)cadmium(II)]-di-μ-seleno-cyanato-κ2 N:Se;κ2 Se:N], [Cd(NCSe)2(C6H7N)2] n (2), suitable for single-crystal X-ray diffraction. The asymmetric unit of compound 1 consists of one Zn cation that is located on a twofold rotation axis as well as one seleno-cyanate anion and one 4-methyl-pyridine ligand in general positions. The Zn cations are tetra-hedrally coordinated by two terminal N-bonding thio-cyanate anions and two 4-methyl-pyridine ligands, forming discrete complexes. The asymmetric unit of compound 2 consists of two crystallographically independent Cd cations, of which one is located on a twofold rotation axis and the second on a center of inversion, as well as two crystallographically independent seleno-cyanate anions and two crystallographically independent 4-methyl-pyridine ligands in general positions. The Cd cations are octa-hedrally coordinated by two N- and two S-bonding seleno-cyanate anions and two 4-methyl-pyridine ligands and are linked into chains by pairs of seleno-cyanate anions. Within the chains, the Cd cations show an alternating cis-cis-trans and all-trans coordination and therefore, the chains are corrugated. PXRD investigations prove that the Zn compound was obtained as a pure phase and that the Cd compound contains a very small amount of an additional and unknown phase. In the IR spectrum of 1, the CN stretching vibration of the seleno-cyanate anion is observed at 2072 cm-1, whereas in the 2 it is shifted to 2094 cm-1, in agreement with the crystal structures.