Wu Lei, Tang Shi-Ya, Zhou Shaodong
Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China.
SINOPEC Research Institute of Safety Engineering, Qingdao 266000, P. R. China.
ACS Omega. 2021 Dec 7;6(50):34904-34911. doi: 10.1021/acsomega.1c05563. eCollection 2021 Dec 21.
Thirty-seven calculation methods were benchmarked against the available experimental bond lengths and energies data regarding the Ag-X bonds. The theoretical protocol PBE0/VDZ//ωB97x-D/mVTZ was found to be capable of accurately predicting the homolytic bond dissociation energies (BDEs) of Ag-X complexes with a precision of 1.9 kcal/mol. With the available method in hand, a wide range of different Ag-X BDEs were estimated. BDE(Ag-CHX), BDE(Ag-PhX), BDE(Ag-OPhX), and BDE(Ag-OCOPhX) (X = NH, OMe, Me, H, Cl, and NO) were found to be in the ranges of 27-47, 51-54, 19-39, and 64-70 kcal/mol, respectively. Subsequently, Hammett-type analysis was carried out with reactivity parameters. Good positive linear relationships were found for BDE of Ag-O bands and decarboxylation barriers of Ag-OCOPhX with the Hammett constant σ. It suggested that electron-donating substituents could promote either the homolytic cleavage of the Ag-OPhX bond to undergo a radical process or Ag-OCOPhX decarboxylation. Moreover, ligand effects on Ag-H bonds were investigated using BDE(Ag-H) and related NPA charges on Ag. In the case of P-ligands, carbene ligands, and other small molecule ligands (i.e., CO, CO, and HO), a good negative linear relationship was found. In contrast, N-ligands could have a reverse effect. Understanding the intrinsic relationships of BDE(Ag-X) with related reactivity parameters might help gain insights into the structure-reactivity relationships in Ag-X-assisted C-H activation/decarboxylation.
针对银 - X键的现有实验键长和能量数据，对37种计算方法进行了基准测试。发现理论方案PBE0/VDZ//ωB97x - D/mVTZ能够精确预测银 - X配合物的均裂键解离能（BDEs），精度为1.9千卡/摩尔。利用手头现有的方法，估算了一系列不同的银 - X BDEs。发现BDE(Ag - CHX)、BDE(Ag - PhX)、BDE(Ag - OPhX)和BDE(Ag - OCOPhX)（X = NH、OMe、Me、H、Cl和NO）分别在27 - 47、51 - 54、19 - 39和64 - 70千卡/摩尔范围内。随后，用反应性参数进行了哈米特型分析。发现银 - O键的BDE和Ag - OCOPhX的脱羧能垒与哈米特常数σ之间存在良好的正线性关系。这表明供电子取代基可以促进Ag - OPhX键的均裂裂解以进行自由基过程或Ag - OCOPhX的脱羧反应。此外，使用BDE(Ag - H)和银上相关的自然键轨道（NPA）电荷研究了配体对银 - H键的影响。对于磷配体、卡宾配体和其他小分子配体（即CO、CO和HO），发现存在良好的负线性关系。相比之下，氮配体可能有相反的效果。了解BDE(Ag - X)与相关反应性参数的内在关系可能有助于深入了解银 - X辅助的C - H活化/脱羧反应中的结构 - 反应性关系。
