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Exceptionally Long C-C Single Bonds in Diamino-o-carborane as Induced by Negative Hyperconjugation
Junxia Li1, Ronglin Pang1, Zhifang Li1
1Hangzhou Normal University, Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, No. 2318 Yuhangtang Rd. Hangzhou, 311121, Zhejiang, China.
Abstract:
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.
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