Synthesis, crystal structures, and thermal properties of new zinc(II) thiocyanato coordination compounds

Abstract

Reaction of zinc(II) thiocyanate with pyrazine, pyrimidine, pyridazine, and pyridine leads to the formation of new zinc(II) thiocyanato coordination compounds. In bis(isothiocyanato-N)-bis(μ2-pyrazine-N,N) zinc(II) (1) and bis(isothiocyanato-N)-bis(μ2-pyrimidine-N,N) zinc(II) (2) the zinc atoms are coordinated by four nitrogen atoms of the diazine ligands and two nitrogen atoms of the isothiocyanato anions within slightly distorted octahedra. The zinc atoms are connected by the diazine ligands into layers, which are further linked by weak intermolecular S···S interactions in 1 and by weak intermolecular C-H···S hydrogen bonding in 2. In bis(isothiocyanato-N)-bis(pyridazine-N) (3) discrete complexes are found, in which the zinc atoms are coordinated by two nitrogen atoms of the isothiocyanato ligands and two nitrogen atoms of the pyridazine ligands. The crystal structure of bis(isothiocyanato-N)-tetrakis(pyridine-N) (4) is known and consists of discrete complexes, in which the zinc atoms are octahedrally coordinated by two thiocyanato anions and four pyridine molecules. Investigations using simultaneous differential thermoanalysis and thermogravimetry, X-ray powder diffraction and IR spectroscopy prove that on heating, the ligand-rich compounds 1, 2, and 3 decompose without the formation of ligand-deficient intermediate phases. In contrast, compound 4 looses the pyridine ligands in two different steps, leading to the formation of the literature known ligand-deficient compound bis(isothiocyanato-N)-bis(pyridine-N) (5) as an intermediate. The crystal structure of compound 5 consists of tetrahedrally coordinated zinc atoms which are surrounded by two isothiocyanato anions and two pyridine ligands. The structures and the thermal reactivity are discussed and compared with this of related transition metal isothiocyanates with pyrazine, pyrimidine, pyridazine, and pyridine. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.