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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >#sigma# Bond Activation by Cooperative Interaction with ns~2 Atoms: Be + nH_2 n = 1-3
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#sigma# 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＃sigma＃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-<:: basis sets have identified and characterized various stationary points on the Be/(Hz)", n = 1-3, hypersurfaces. The van der Waals complexes, Be(Hz)", are very weakly bound (De = 0.08-0.32 kcal/mol with respect to Hz Joss) with Hz/Hz interactions playing an important role in detenri.ining equilibrium structures which can be understood in terms of the various relevant long-range potentials. The covalent molecule, BeHzo is found to have a linear, centrosymmetric structure and to be strongly bound with respect to Be + Hz, in agreement with previous calculations. Be Hz Interacts weakly with additional Hz molecules (De < 0, 75 kcal/mol) which are positioned parallel to the nearJinear Be Hz moiety in the equilibrium structures of the BeHz(Hz)n-l complexes. Of particular interest is the dramatic change in the nature of the transitioq state for Be Hz production depending on the number of Hz molecules present. For n = 1, the reaction proceeds stepwise: flrstbreaking the Hz bond and forming one BeH bond followed 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 Hz bonds are broken while simultaneously two BeH bonds and one new H2 bond are formed. The activation energy for this process decreases from the n = 1 value to about 38 kcaVmol. For n = 3, the reaction proceeds through a true insertion mechanism with the addition of the third Hz molecule, decreasing the activation energy to about 33 kcaVmol. The results are discussed in comparison to the isoelectronic B+lnHz systems where significant a bond activation through a cooperative interaction mechanism has been identified.
机译：从MP2，CCSD（T）和MRCISD的理论水平进行的从头开始研究，具有增强的Triple- ::基集，已识别并表征了Be /（Hz）“，n = 1-3，超表面上的各种固定点。范德华络合物Be（Hz）“的结合非常弱（相对于Hz Joss，De = 0.08-0.32 kcal / mol），而Hz / Hz相互作用在确定平衡结构中起着重要作用。在各种相关的远程潜力方面。与先前的计算一致，发现共价分子BeHzo具有线性，中心对称的结构，并且相对于Be + Hz具有牢固的结合力。 Be Hz与平行于BeHz（Hz）n-1配合物平衡结构中近近的Be Hz部分定位的其他Hz分子（De <0，75 kcal / mol）弱相互作用。特别令人关注的是，取决于存在的Hz分子的数量，Be Hz产生的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Hz键，形成一个BeH键，然后形成第二个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状态进行，其中两个Hz键断裂，同时同时形成两个BeH键和一个新的H2键。此过程的活化能从n = 1降低到约38 kcaVmol。对于n = 3，反应通过添加第三Hz分子的真实插入机理进行，从而将活化能降至约33 kcaVmol。与等电B + lnHz系统相比，对结果进行了讨论，在等电B + lnHz系统中，通过协同相互作用机制显着地激活了键。

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