N-Heterocyclic Carbenes with a Nido-C2B9 Carborane Backbone
N-Heterocyclic Carbenes with a Nido-C2B9 Carborane Backbone
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具有 Nido-C2B9 碳硼烷主链的 N-杂环卡宾
DOI：
10.1002/cjoc.202100302
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发表时间：
2021
影响因子：
5.4
通讯作者：
Xiao Xu-Qiong
中科院分区：
文献类型：
--
作者：
Wang Beining;Cui Zhongzheng;Li Junxia;Pang Ronglin;Kang Yanrui;Xiao Xu-Qiong
主要观察和结论N-杂环卡宾(NHCs)的空间和电子性质可通过氮原子上的外环取代基、5元咪唑骨架的1-3个原子的取代和主链的变化来改变。在此，我们报道了NIDO-C2B9Carborane阴离子作为NHCS的骨架的使用。搅拌仲氨基碳硼烷(1b-1e)、原甲酸三乙酯和HbF4∙Et2O的混合物，导致邻碳硼烷意外开笼，得到N-杂环卡宾前体(4b-4e)负载的N-硝基-C2B9Carborane阴离子。在−780C下，4b与六甲基二硅氮化钠去质子化得到杂环卡宾配体，它被用来形成Au(I)NHC络合物(5)。密度泛函理论计算揭示了卡宾配体的一对高位孤立轨道，预测了它们强大的σ捐献能力。
Main observation and conclusionThe steric and electronic properties ofN‐heterocyclic carbenes (NHCs) can be modified by the exocyclic substituents at the nitrogen atoms, by 1—3 atoms’ replacements of the five‐membered imidazolium skeleton and by the changes of the backbones. Herein, we report the usage ofnido‐C2B9carborane anions as the backbones of NHCs. Stirring the mixture of secondary aminoo‐carboranes (1b—1e), triethyl orthoformate and HBF4∙Et2O results in the unexpected cage‐opening ofo‐carboranes to afford thenido‐C2B9carborane anions supportedN‐heterocyclic carbene precursors (4b—4e). Deprotonation of 4b with sodium hexamethyldisilazide at −78oC affords theN‐heterocyclic carbene ligand, which was used to form an Au(I) NHC complex (5). DFT calculations revealed a high‐lying lone pair orbitals of the carbene ligands, predicting their strong σ‐donating abilities.