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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >σ Bond Activation by Cooperative Interaction with ns~2 Atoms: Be + nH_2, n = 1-3
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σ Bond Activation by Cooperative Interaction with ns~2 Atoms: Be + nH_2, n = 1-3

机译：通过与ns〜2个原子的协作相互作用来激活键：Be + nH_2，n = 1-3

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摘要

Ab initio investigations at the MP2, CCSD(T), and MRCISD levels of theory with augmented triple-ξ basis sets have identified and characterized various stationary points on the Be/(H_2)_n, n = 1-3, hypersurfaces. The van der Waals complexes, Be(H_2)_n, are very weakly bound (D_e = 0.08-0.32 kcal/mol with respect to H_2 loss) with H_2/H_2 interactions playing an important role in determining equilibrium structures which can be understood in terms of the various relevant long-range potentials. The covalent molecule. BeH_2, is found to have a linear, centrosymmetric structure and to be strongly bound with respect to Be + H_2, in agreement with previous calculations. BeH_2 interacts weakly with additional H_2 molecules (D_e < 0.75 kcal/mol) which are positioned parallel to the near-linear BeH_2 moiety in the equilibrium structures of the BeH_2(H_2)_(n-1) complexes. Of particular interest is the dramatic change in the nature of the transition state for BeH_2 production depending on the number of H_2 molecules present. For n = 1, the reaction proceeds stepwise: first breaking the H_2 bond and forming one BeH bond flowed by forming the second BeH bond. This process has an activation energy of about 56 kcal/mol. For n = 2, the reaction proceeds via a pericyclic mechanism through a planar cyclic transition state where two H_2 bonds are broken while simultaneously two BeH bonds and one new H_2 bond are formed. The activation energy for this process decreases from the n = 1 value to about 38 kcal/mol. For n = 3, the reaction proceeds through a true insertion mechanism with the addition of the third H_2 molecule, decreasing the activation energy to about 33 kcal/mol. The results are discussed in comparison to the isoelectronic B~+H_2 systems where significant σ bond activation through a cooperative interaction mechanism has been identified.
机译：在MP2，CCSD（T）和MRCISD的理论水平上，具有增强的Triple-ξ基集的从头算研究已经确定并表征了Be /（H_2）_n，n = 1-3，超曲面上的各种固定点。范德华络合物Be（H_2）_n与H_2 / H_2的相互作用非常弱（对于H_2的损失D_e = 0.08-0.32 kcal / mol），在确定平衡结构方面起着重要的作用。各种相关的远程潜力。共价分子。与先前的计算相一致，发现BeH_2具有线性，中心对称的结构，并且相对于Be + H_2具有强约束力。 BeH_2与其他H_2分子（D_e <0.75 kcal / mol）弱相互作用，这些分子平行于BeH_2（H_2）_（n-1）络合物的平衡结构中的近线性BeH_2部分。特别令人感兴趣的是，取决于存在的H_2分子的数量，BeH_2生成过渡态的性质发生了巨大变化。对于n = 1，反应逐步进行：首先破坏H_2键，并通过形成第二个BeH键形成一个流动的BeH键。该过程具有约56kcal / mol的活化能。对于n ＝ 2，反应通过周环机制通过平面环状过渡态进行，其中两个H_2键断裂，同时同时形成两个BeH键和一个新的H_2键。此过程的活化能从n = 1降低到约38 kcal / mol。对于n ＝ 3，反应通过添加第三H_2分子的真实插入机理进行，从而将活化能降低至约33kcal / mol。与等电B〜+ / nH_2系统进行了比较，讨论了等电B〜+ / nH_2系统通过协同相互作用机制显着激活σ键的作用。

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