Li Junxia, Pang Ronglin, Li Zhifang, Lai Guoqiao, Xiao Xu-Qiong, Müller Thomas
Hangzhou Normal University, Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, No. 2318 Yuhangtang Rd. Hangzhou, 311121, Zhejiang, China.
Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl-von-Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany.
Angew Chem Int Ed Engl. 2019 Jan 28;58(5):1397-1401. doi: 10.1002/anie.201812555. Epub 2018 Dec 7.
The synthesis of a series of 1,2-diamino-o-carboranes (1-4) is reported. The molecular structures of these diamino-o-carboranes are remarkable as the inner-cluster C-C bonds are all ultra-long (162.7-193.1 pm) and vary substantially with small variations in the substituents. The results of quantum mechanical investigations suggest that the origin of the bond elongation is significant in-plane negative hyperconjugation of lone pairs of the nitrogen substituents with the σ* orbitals of the C-C bonds in o-carboranes.
报道了一系列1,2-二氨基邻碳硼烷（1-4）的合成。这些二氨基邻碳硼烷的分子结构很显著，因为簇内C-C键均超长（162.7 - 193.1 pm），并且会随着取代基的微小变化而大幅改变。量子力学研究结果表明，键伸长的起源是氮取代基孤对电子与邻碳硼烷中C-C键的σ*轨道发生显著的面内负超共轭作用。
