Computational study on C-B homolytic bond dissociation enthalpies of organoboron compoundsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6nj02887j

• Main Authors: Wang, JiaoYang, Zheng, WenRui, Ding, LanLan, Wang, YingXing
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c6nj02887j

Based on many transition-metal-catalyzed Suzuki-Miyaura cross-coupling reactions of organoboron compounds in which C-B cleavages are involved, it is meaningful to understand one of the thermodynamic properties of the C-B bond, the strength of the C-B bond, which can be measured using homolytic bond dissociation enthalpies (BDEs). To this end, we first calculated 64 C-B BDEs of organoboron compounds by theoretical methods including composite high-level ab initio methods of G3, G4, G3B3, CBS-Q, CBS-QB3, and CBS-4M and 34 density functional theory (DFT) methods. The results show that it is reasonable and credible to regard the average values of six composite high-level methods as the standard C-B BDE values. By comparing the DFT methods, it is found that the M06-HF method provides the most accurate results and the root mean square error (RMSE) is the smallest of 6.4 kJ mol −1 . Therefore, the C-B BDEs including C(sp)-B, C(sp 2 )-B and C(sp 3 )-B of organoboron compounds such as boronic acids, trifluoroborate salts, boronate esters, etc. as well as the substituent effects were investigated by using the M06-HF method. The results indicated that the different substituents including electron-donating groups (EDGs), electron-withdrawing groups (EWGs) and conjugated effect groups (CEGs) exhibit different effects on different types of C-B BDEs. Moreover, the natural bond orbital (NBO) analysis was performed in order to further disclose the essence of BDE change patterns. The theoretical study of three hybridized C-B BDEs with different substituents can provide corresponding guidance to experimental research studies.