Hexaaquacobalt(II) and hexaaquacadmium(II) 4-nitro-2,3,5,6-tetraoxopyridinates [M(H2O)6](C5HN2O6)2 · 2H2O (M = Co and Cd): Synthesis, structures, and properties

Abstract

The complexes [Cd(H2O)6](C5HN2O6)2 · 2H2O (I) and [Co(H2O)6](C5HN2O6)2 · 2H2O (II) were obtained in the crystalline state by reactions of cobalt chloride and cadmium chloride with ammonium 4-nitro-2,3,5,6-tetraoxopyridinate, (NH4)2 · (C5HO6N2)2. Their cocrystallization gave the heterometallic complex [Cd0.32Co0.68(H2O)6](C5HN2O6)2 · 2H2O (III). The crystal and molecular structures of complexes I-III were determined by X-ray diffraction. It was demonstrated that the complexation reactions occur by replacement of two ammonium cations 4-nitro-2,3,5,6-tetraoxopyridinate by the complex cations [M(H2O)6]2+. The tetraoxopyridinate anions and the complex cations are hydrogen-bonded through the coordinated and crystallization water molecules as well as through the O atoms of the organic anion. The thermolysis of complexes I and II was examined by TGA.