Synthesis, Characterization and Thermal Decomposition of the Pyridine Adducts of Co, Ni, Cu and Zn Sulfate

Abstract

Pyridine adducts of Co, Ni, Cu and Zn sulfate were obtained by refluxing the corresponding sulfate with pyridine in chloroform. The compounds were characterized by elemental analysis, X-ray powder diffraction and FTIR spectroscopy. The thermal decompositions (TG/DTG/DTA) of the complexes in the interval 20-1000°C were also studied. The elemental and thermal analysis results revealed that the formulae of the complexes are M 2 (SO 4 ) 2 xC 5 H 5 N.yH 2 O, where x=2, 3, 2 and 1 and y=6, 4, 6 and 4 for the Co, Ni, Cu and Zn compound, respectively. The complexes were not found to be isostructural, but certain structural similarities were observed between the Zn and Co compounds. Although the thermal decomposition pathways of the various compounds were quite different and each consisted of several steps, in all cases the dehydration preceded the depyridination. Metal oxide was always obtained as final product. The spectral data are discussed with regard to the thermal behaviour. Appreciably strong hydrogen-bonding and pronounced structural differences relating to the sulfate ions were presumed for the Cu compound.