Thermal Dehydration and Decomposition of Dioxalato Complexes of Be(II), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) in Solid State

Abstract

The structures of anhydrous dioxalato complexes K2[M(C2O4)2] (M: Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) prepared by heating their hydrates, were examined by means of infrared absorption and visible reflectance spectroscopy. It was found that the anhydrous complexes of Mn(II), Co(II), and Zn(II) exist in a polynuclear octahedral form with a bridging oxalate group, and those of Ni(II) and Cu(II), in a monomer form. On further heating, the complexes of Be(II), Mn(II), and Zn(II) decomposed into the corresponding metal oxides and potassium oxalate, and those of Co(II), Ni(II), and Cu(II) into the corresponding metals and potassium oxalate. Except for the beryllium(II) complex, the complexes decomposed at lower temperatures with an increase in 1/r, where r is the radius of metal ion.