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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mechanisms of Hydrogen Generation from Tetrameric Clusters of Lithium Amidoborane
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Mechanisms of Hydrogen Generation from Tetrameric Clusters of Lithium Amidoborane

机译：酰胺基硼烷锂四聚体团簇产生氢的机理

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摘要

The first-principles study of dehydrogenation mechanism of tetrameric clusters of lithium amidoborane LiNH2BH3, (LiAB)(4), is presented. The choice of tetramer is based on the suspicion that dimeric cluster models used in previous theoretical studies are too small to capture the essence of the reaction. Dehydrogenation pathways starting from three isomers of (LiAB)(4) tetramers were explored by applying the artificial force induced reaction (AFIR) method at the M06 level of theory. All obtained reaction pathways feature initial dimerization of two LiAB molecules in the tetramer. Formation of intermediates containing the Li3H moiety is a very characteristic feature of all pathways. In the succeeding rate-limiting step of the release of H-2 molecule, a hydridic H atom of the Li3H moiety activates a protic H atom of the NH2 group with formation of the Li2H2 moiety in transition state. The most kinetically favorable pathway has the activation enthalpy of 26.6 kcal mol(-1), substantially lower than that found for dimeric cluster. The obtained results suggest that only three LiAB molecules directly participate in the elementary reactions.
机译：提出了第一原理研究酰胺基硼烷锂LiNH2BH3（LiAB）（4）的四聚体簇的脱氢机理。选择四聚体是基于以下怀疑：先前的理论研究中使用的二聚体簇模型太小，无法捕获反应的本质。通过在理论上的M06水平应用人工诱导反应（AFIR）方法探索了从（LiAB）（4）四聚体的三个异构体开始的脱氢途径。所有获得的反应途径均以四聚体中两个LiAB分子的初始二聚为特征。包含Li 3 H部分的中间体的形成是所有途径的非常特征性的特征。在释放H-2分子的后续限速步骤中，Li3H部分的氢化H原子激活NH2基的质子H原子，并形成过渡态的Li2H2部分。最动力学上有利的途径具有26.6 kcal mol（-1）的活化焓，大大低于二聚体簇的活化焓。获得的结果表明，只有三个LiAB分子直接参与基本反应。

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