The thermal decomposition reactions of MC4H4O4 (M : Mg(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II)) in nitrogen or helium were investigated by means of TG-DTA, X-ray diffraction measurements, gas chromatography, and combustion analysis for carbon. The decomposition residues of the Mg and Zn salts were composed of the corresponding metal oxides and some carbon, while those of the Co, Ni, Cu, and Pb salts were composed of the corresponding metals and some carbon. H2, O2, CO, CO2, H2O, CH4, C2H2, C2H4, HCOOCH3, HCOOC2H5, CH3COOC2H5, C2H5COOC2H5, and (CH2CO)2O were identified as the gaseous decomposition products; the compositions of the gaseous mixtures varied a great deal with the metals. Possible reaction mechanisms were discussed mainly on the basis of the decomposition products.
The stoichiometry of thermal dehydration of MX2(hmta)2·nH2O (hmta=hexamethylenetetramine; X= Cl−, Br−, I−, NO3−, NCS−; n=4–10) was established by the TG-DTA methods. The nature of the structural changes caused by complete or partial dehydration was studied on the basis of the accompanying changes in the electronic and vibrational spectra. Anions and hmta in general get into the coordination sphere with a decrease in the number of the coordinated water, but the bulky and weakly basic amine often gets coordinated in the last stage.
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