SYNTHESIS AND STRUCTURE OF BIS(XYLARATO )GERMANATES OF MAGNESIUM, CALCIUM AND BARIUM

A procedure for the synthesis of the heterometallic germanium(IV) and magnesium, calcium and barium complexes with xylaric acid (H5Xylar) [Ge(μ-HXylar)2{Mg(Н2О)2}2]·4H2O(І), [Ge(μ-HXylar)2{Ca(Н2О)2}2]·3H2O(ІІ), [Ge(μ-HXylar)2{Ba(Н2О)4}2]·3H2O(ІІІ) were developed and the complexes isolated for the first time in the solid state. The first stage of synthesis portions of GeО2 (2.092 g, 0.02 mol) and xylaric acid С5H8О7 (7.2 g, 0.04 mol) were inserted in hot water (500 ml), heated (рН 1,5-2) and concentrated on a water bath to 150 ml (~4.5 h). Then the resulting solution was cooled to room temperature and MgCO3 (І), СаСO3 (ІІ) or ВаCO3 (ІІІ) added to рН=5. The heteronuclear coordination compounds were characterized by elemental analysis, powder X-ray diffraction, thermogravimetry, IR spectroscopy. Complexes I-III are X-ray amorphous compound with the molar ratio Mg(Ca, Ba) : Ge : ligand = 2 : 1 : 2. A study of the thermal stability of complexes has shown that its thermolysis is stepwise. Analysis of the IR spectra of complexes І-III showed that spectrums does not contain bands at 3590-3650 cm-1 and ν(С=О) = 1720 cm-1 typical of stretching vibrations of free OH and COOH. Bands detected at ν(С–О)~1000-1139 cm-1 typical of alkoxides, and nas(СОО–)~1678-1684 and ns(СОО–)~1356-1413 cm-1 of carboxylate ions. The scheme of structure of compounds I-IІІ was offered