College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, Beijing, 100049, China.
Inorg Chem. 2010 Jan 4;49(1):295-301. doi: 10.1021/ic902039g.
In this study, a strategy to design a metal-free hydrogen activation site has been proposed. On the basis of our so-called sp(3) carbon bridged FLPs (Frustrated Lewis Pairs), we first hypothesized that a more reactive activation site should arrange the nitrogen lone pair and the boron vacant orbital to lie in the same plane face-to-face, because such orbital orientations can simultaneously enhance the interaction between the nitrogen lone pair and the H(2) sigma* antibonding orbital and the interaction between the boron vacant orbital and the H(2) sigma bonding electrons. To verify that such an active site is achievable, we then computationally designed molecules and studied their reactions with hydrogen. The energetic results show the designed molecules are indeed more reactive than the sp(3) carbon bridged FLPs. Some of the hydrogen activations reach kinetics and thermodynamics comparable with those of the hydrogen activations mediated by the well-known metal-ligand bifunctional hydrogenation catalysts. The designed molecules could be the targets for experimental synthesis. The pattern of the proposed active site can be based to design similar molecules for metal-free hydrogenations.
在这项研究中，提出了一种设计无金属氢活化位点的策略。基于我们所谓的 sp(3)碳桥接 FLP（受阻路易斯对），我们首先假设更具反应性的活化位点应安排氮孤对和硼空轨道位于同一平面面对面，因为这种轨道取向可以同时增强氮孤对与 H(2)sigma*反键轨道和硼空轨道与 H(2)sigma 成键电子之间的相互作用。为了验证这样的活性位点是可行的，我们随后通过计算设计了分子并研究了它们与氢气的反应。能量结果表明，设计的分子确实比 sp(3)碳桥接 FLP 更具反应性。一些氢的活化达到了与由著名的金属配体双功能加氢催化剂介导的氢活化相当的动力学和热力学。设计的分子可能是实验合成的目标。所提出的活性位点的模式可以用来设计用于无金属加氢的类似分子。
