【摘要】 以气相色谱为主要手段,测定了25种草酸配位化合物的热稳定性,得到了许多差热分析和热失重方法所得不到的信息。二价金属草酸盐的热分解可分为三种类型:产生CO₂和金属,产生CO,CO₂和金属氧化物以及产生CO和金属碳酸盐。某些草酸盐的热分解同时按其中的两种类型进行。草酸配位化合物分解CO₂峰值温度随中心离子标准电极电位增加而降低,大致有线性关系t_p=-86.2E₁⁰+273（℃）。还对二价金属草酸盐进行了理论计算,讨论了电子结构与热稳定性的关系。更多还原

【Abstract】 In this paper the thermal stabilities of 25 oxalato coordination compounds have been studies mainly by gas chromatography.Information which can not be obtained from TG or DTA has been obtained by this method.The principal findings may be summarized as follows: 1.When the thermal decomposition of the oxalato complexes of various metals was carried out in helium,the crystalization and the coordination water were expelled.Thermal decomposition in hydrogen gave additional water as a result of the reduction of CO and CO₂ as well as of the metal oxide （Fig.8）.The temperatures of dehydration of MC₂O₄·2H₂O（M=Mn,Ni,Fe,Co,Zn etc.） depended on the nature of the cations.An empirical equation giving relationship between the peak value of decomposition temperature and the ionic potential of the cation has been proposed: t_p（℃）=72.7（Z/r）-14 2.The thermal decomposition reactions of bivalent metal oxalates may be divided into three types: （1） MC₂O₄→M+2CO₂（e.g.,M=Co,Cu,Ni and Hg;Fig.9A）;（2） MC₂O₄→MO+CO+CO₂ （e.g.,M=Fe,Mn,Zn,etc.; Fig.9B）;（3） MC₂O₄→MCO₃+CO（e.g.,M=Ca etc.;Fig.9C）.In a few cases of bivalent metal oxalates,such as CoC₂O₄,CuC₂O₄ and NiC₂O₄,thermal decomposition took place according to types （1） and （2） simultaneously,although with （1） predominant,that is,their decomposition products not only contained CO₂,but also a little CO.In addition,CaC₂O₄ decomposed according to both types （2） and （3） with the latter dominating.There were two types of the thermal decomposition reactions of the trivalent metal oxalates: （1） M₂（C₂O₄）₃→2MC₂O₄+2CO₂, then MC₂O₄→MO+CO+CO₂ （e. g., M=Fe; Fig. 10D）. The analysis of X-ray diffraction pattern showed the initial solid product of thermal decomposition of Fe₂ （C₂O₄）₃ was FeC₂O₄ （Fig. 4）; （2） M₂（C₂O₄）₃→M₂O₃+3CO+3CO₂（e. g., M=Al; Fig. 10E）. 3. An approximate equation to correlate the peak value of the decomposition to give CO₂ with the electrode potential of the metal has been suggested: t_p（°C）= -86.2E₁⁰+273. When E₁⁰<-0.44V, the metal ion could be reduced, producing CO². When E₁⁰<-0.44V, the metal ion could not be reduced, and the self redox reaction took place within C₂₀₄²-, yielding CO and CO₂ as well as CO and carbonate. This critical experimental value E₁⁰-0.44V is quite close to the standard electrode potential of C₂₀₄²-（E₂⁰=-0.49 V）. It was shown that the more negative was the electrode potential of the metal ion, the higher temperature of the thermal decomposition would be. Therefore the equation was derived: △G=-nF（E₁⁰-E₂⁰） as a semi-quantitative criterion of thermal decomposition of the metal oxalates without considering the hydration in solution. 4. According to the results of calculation by EHMO method,experimental findings of the thermal decomposition of some bivalent metal oxalates have been explained The thermal stabilities of oxalates of bivalent metals increased with the increase of. the positive charges on the metals （δ_m⁺） and the atomic overlap population of C—C （Pcc） and with the decrease of the positive charges on carbon atom. When P_co₁ was large and δ_m⁺ small, ruptures of C—C and M—O took place easily, producing CO₂ and the free metal (e. g. CuC₂₀₄). When P_co₁ was small and δ_m⁺ large, ruptures of C—C and C—O₁ were dominant, yielding CO and the metal carbonate (e.g. CaC₂₀₄). In the intermediate cases, ruptures of C—C and part of C—O₁, and M—O₁ were possible, producing CO, CO₂ and the metal oxide (e. g. MnC₂₀₄).更多还原