Synthesis, Structural Characterization, and Thermal Decomposition Study of Mg(H2O)6B10H10路4H2O

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• 作者：Teshome B. Yisgedu ; Xuenian Chen ; Hima K. Lingam ; Zhenguo Huang ; Aaron Highley ; Sean Maharrey ; Richard Behrens ; Sheldon G. Shore ; Ji-Cheng Zhao
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：June 16, 2011
• 年：2011
• 卷：115
• 期：23
• 页码：11793-11802
• 全文大小：1159K
• 年卷期：v.115,no.23(June 16, 2011)
• ISSN：1932-7455

文摘

Compound 1 (Mg(H₂O)₆B₁₀H₁₀路4H₂O) was synthesized and characterized using NMR, IR, XRD, and elemental analysis. Its thermal decomposition behavior was studied using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS), TGA, DSC, IR, and ¹¹B NMR. The crystal structure of 1 reveals multiple dihydrogen and hydrogen bonding interactions that form a 3D extended structure. A reaction network characterizing the thermal decomposition of 1 and its secondary products over a temperature range from 20 to 1000 掳C has been developed. Thermal decomposition of 1 is primarily controlled by two competing branches in the reaction network, where coordinated water evolves as either H₂O (dehydration) or H₂ (dehydrogenation). The extent of reaction to form H₂ depends on the fraction of the coordinated water remaining in the sample when its temperature is between 160 and 225 掳C. The evolution of coordinated water is reversible and controlled by dissociative sublimation. For the release of coordinated water between 160 and 215 掳C, the vapor pressure of water is given by Log_eP (Torr) = 30.4561 鈥?12425.2/T (K) and 螖H_s = 103.3 卤 0.3 kJ/mol. The nature of the condensed phase secondary product remaining after all coordinated water is removed by either dehydration and/or dehydrogenation depends strongly on the extent of reaction to form Mg(OH)_xB₁₀H_10鈥?i>x. Results of STMBMS experiments where x varies from 0.2 to 4 are used to develop the reaction network that characterizes the thermal decomposition process. Heating of 1 at 205 掳C resulted in the formation of water-soluble Mg(OH)_x(H₂O)_2鈥?i>xB₁₀H_10鈥?i>x, while prolonged heating of 1 at 270 掳C and heating up to 1000 掳C led to decomposition.