State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China.
J Phys Chem A. 2012 Mar 15;116(10):2583-90. doi: 10.1021/jp212319p. Epub 2012 Mar 6.
The hydrogen-transfer reaction of W + NH(3) incorporates four possible diabatic reaction pathways along with septet, quintet, triplet, and singlet states. The intersystem crossings thus play an important role in the reaction mechanisms. In this work, ab initio and DFT methods are used to determine all possible intermediates, transition states, products, and intersystem crossing points as well as the spin-orbit couplings. The mechanism of hydrogen elimination is further revealed by the natural bond orbital analysis. From the rate constants yielded by a nonadiabatic transition state theory, we find that two intersystem crossings significantly change the reaction pathways. Finally, we suggest a feasible reaction pathway with exothermicity 72.8 kcal/mol, which is consistent with the experimental measurements.
W+NH(3)的氢转移反应包含四条可能的非绝热反应途径，以及七重态、五重态、三重态和单重态。因此，系间窜越在反应机制中起着重要作用。在这项工作中，我们使用从头算和密度泛函理论方法来确定所有可能的中间体、过渡态、产物和系间窜越点以及自旋轨道耦合。通过自然键轨道分析进一步揭示了氢消除的机制。根据非绝热过渡态理论得出的速率常数，我们发现两个系间窜越显著改变了反应途径。最后，我们提出了一条可行的反应途径，其放热性为 72.8 kcal/mol，与实验测量结果一致。
