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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Computational study of the release of H-2 from ammonia borane dimer (BH3NH3)(2) and its ion pair isomers
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Computational study of the release of H-2 from ammonia borane dimer (BH3NH3)(2) and its ion pair isomers

机译：氨硼烷二聚体（BH3NH3）（2）及其离子对异构体释放H-2的计算研究

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High-level electronic structure calculations have been used to map out the relevant portions of the potential energy surfaces for the release of H-2 from dimers of ammonia borane, BH3NH3 (AB). Using the correlation-consistent aug-cc-pVTZ basis set at the second-order perturbation MP2 level, geometries of stationary points were optimized. Relative energies were computed at these points using coupled-cluster CCSD(T) theory with the correlation-consistent basis sets at least up to the aug-cc-pVTZ level and in some cases extrapolated to the complete basis set limit. The results show that there are a number of possible dimers involving different types of hydrogen-bonded interactions. The most stable gaseous phase (AB)(2) dimer results from a head-to-tail cyclic conformation and is stabilized by 14.0 kcal/mol with respect to two AB monomers. (AB)(2) can generate one or two H-2 molecules via several direct pathways with energy barriers ranging from 44 to 50 kcal/mol. The diammoniate of diborane ion pair isomer, [BH4-][NH3BH2NH3+] (DADB), is 10.6 kcal/mol less stable than (AB)(2) and can be formed from two AB monomers by overcoming an energy barrier of similar to 26 kcal/mol. DADB can also be generated from successive additions of two NH3 molecules to B2H6 and from condensation of AB with separated BH3 and NH3 Molecules. The pathway for H-2 elimination from DADB is characterized by a smaller energy barrier of 20.1 kcal/mol. The alternative ion pair [NH4+][BH3NH2BH3-] is calculated to be 16.4 kcal/mol above (AB)(2) and undergoes H-2 release with an energy barrier of 17.7 kcal/mol. H-2 elimination from both ion pair isomers yields the chain BH3NH2BH,NH3 as product. Our results suggest that the neutral dimer will play a minor role in the release of H-2 from ammonia borane, with a dominant role from the ion pairs as observed experimentally in ionic liquids and the solid state.
机译：已使用高级电子结构计算来绘制势能表面的相关部分，以从氨硼烷BH3NH3（AB）的二聚体释放H-2。使用在二阶扰动MP2级别上设置的相关一致的aug-cc-pVTZ基，优化了固定点的几何形状。相对能量是使用耦合簇CCSD（T）理论在这些点上计算的，其中相关一致的基集至少可以达到aug-cc-pVTZ水平，在某些情况下可以推算到完整的基集极限。结果表明，存在许多可能的涉及不同类型氢键相互作用的二聚体。最稳定的气相（AB）（2）二聚体由头到尾的环状构象产生，相对于两种AB单体稳定在14.0 kcal / mol。 （AB）（2）可以通过几种直接途径生成一个或两个H-2分子，其能垒范围为44至50 kcal / mol。乙硼烷离子对异构体的二苯甲酸酯[BH4-] [NH3BH2NH3 +]（DADB）的稳定性比（AB）（2）低10.6 kcal / mol，可以通过克服类似于26的能垒由两种AB单体形成大卡/摩尔DADB也可以通过向B2H6中连续添加两个NH3分子以及AB与分离的BH3和NH3分子的缩合生成。从DADB中消除H-2的途径的特征在于较小的20.1 kcal / mol的能垒。计算得出替代离子对[NH4 +] [BH3NH2BH3-]比（AB）（2）高16.4 kcal / mol，并以17.7 kcal / mol的能垒进行H-2释放。从两个离子对异构体的H-2消除生成BH3NH2BH，NH3链作为产物。我们的结果表明，中性二聚体在氨硼烷中释放H-2时起较小作用，而在离子液体和固态中通过实验观察到的离子对起主要作用。

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