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

Abstract

The reactions of Zn(NO3)2 .6H2O and Cd(NO3)2 .4H2O with KSeCN and 4-methylpyridine (C6H7N; 4-picoline) lead to the formation of crystals of bis(4-methylpyridine-κN)bis(selenocyanato-κN)zinc(II), [Cd(NCSe)2(C6H7N)2] (1), and catena-poly[[bis(4-methylpyridine-κN)cadmium(II)]-di-μ-selenocyanato-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 selenocyanate anion and one 4-methylpyridine ligand in general positions. The Zn cations are tetrahedrally coordinated by two terminal N-bonding thiocyanate anions and two 4-methylpyridine 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 selenocyanate anions and two crystallographically independent 4-methylpyridine ligands in general positions. The Cd cations are octahedrally coordinated by two N- and two S-bonding selenocyanate anions and two 4-methylpyridine ligands and are linked into chains by pairs of selenocyanate 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 selenocyanate anion is observed at 2072 cm−1, whereas in the 2 it is shifted to 2094 cm−1, in agreement with the crystal structures.