Gnanasekar Sharon Priya, Arunan Elangannan
Department of Inorganic and Physical Chemistry , Indian Institute of Science , Bangalore 560012 , India.
J Phys Chem A. 2019 Feb 14;123(6):1168-1176. doi: 10.1021/acs.jpca.8b09778. Epub 2018 Nov 15.
Atoms in molecules (AIM), natural bond orbital (NBO), and normal coordinate analysis have been carried out at the global minimum structures of TH (T = C/Si/Ge). All these analyses lead to a consistent structure for these three protonated TH molecules. The CH has a structure with three short and two long C-H covalent bonds and no H-H bond. Hence, the popular characterization of protonated methane as a weakly bound CH and H is inconsistent with these results. However, SiH and GeH are both indeed a complex formed between TH and H stabilized by a tetrel bond, with the H being the tetrel bond acceptor. The three-center-two-electron bond (3c-2e) in CH has an open structure, which can be characterized as a V-type 3c-2e bond and that found in SiH and GeH is a T-type 3c-2e bond. This difference could be understood based on the typical C-H, Si-H, Ge-H, and H-H bond and the tetrel bond energies. This analysis explains the trend observed in proton affinity of TH which appears counterintuitive GeH > SiH > CH. Carbon is selective in forming a "tetrel bond" and when it does, it might be worthwhile to highlight it as a "carbon bond".
已在TH（T = C/Si/Ge）的全局最小结构上进行了分子中的原子（AIM）、自然键轨道（NBO）和简正坐标分析。所有这些分析都得出了这三种质子化TH分子的一致结构。CH具有一个结构，其中有三个短的和两个长的C-H共价键，且没有H-H键。因此，将质子化甲烷普遍表征为弱结合的CH和H与这些结果不一致。然而，SiH和GeH确实都是由TH和H之间通过四元键稳定形成的复合物，其中H是四元键受体。CH中的三中心两电子键（3c-2e）具有开放结构，可表征为V型3c-2e键，而在SiH和GeH中发现的是T型3c-2e键。这种差异可以基于典型的C-H、Si-H、Ge-H和H-H键以及四元键能来理解。该分析解释了在TH的质子亲和性中观察到的看似违反直觉的趋势：GeH > SiH > CH。碳在形成“四元键”时具有选择性，当它形成时，将其突出为“碳键”可能是值得的。
