Fusing N-Heterocyclic Carbenes with Carborane Anions**
Fusing N-Heterocyclic Carbenes with Carborane Anions**
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DOI：
10.1002/anie.201402445
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发表时间：
2014-04-22
影响因子：
16.6
通讯作者：
Lavallo, Vincent
中科院分区：
文献类型：
--
作者：
El-Hellani, Ahmad;Lavallo, Vincent
在这里，我们描述了两个不寻常的含碳分子家族的融合，它们很容易忽视碳形成四个化学键的趋势，即n-杂环碳烯（NHCs）和碳硼烷阴离子。阴离子咪唑盐与二异丙酰胺锂在室温下进行脱质子反应，得到C-2和C-5二阴离子NHC构象异构体的锂配合物以及三阴离子（C-2, C-5）加合物的混合物。明智地选择碱和反应条件，可以选择性地形成所有三种稳定的聚阴离子羰基。在溶液中，所谓的异常C-5 NHC锂配合物缓慢异构化为正常的C-2 NHC，该过程可以通过阴离子咪唑盐的加入进行质子催化。这些结果表明，两种不寻常形式的碳原子的结合可以导致意想不到的化学行为，这一策略为开发新一代用于催化的NHC配体铺平了道路。
Here we describe the fusion of two families of unusual carbon-containing molecules that readily disregard the tendency of carbon to form four chemical bonds, namely N-heterocyclic carbenes (NHCs) and carborane anions. Deprotonation of an anionic imidazolium salt with lithium diisopropylamide at room temperature leads to a mixture of lithium complexes of C-2 and C-5 dianionic NHC constitutional isomers as well as a trianionic (C-2, C-5) adduct. Judicious choice of the base and reaction conditions allows the selective formation of all three stable polyanionic carbenes. In solution, the so-called abnormal C-5 NHC lithium complex slowly isomerizes to the normal C-2 NHC, and the process can be proton-catalyzed by the addition of the anionic imidazolium salt. These results indicate that the combination of two unusual forms of carbon atoms can lead to unexpected chemical behavior, and that this strategy paves the way for the development of a broad new generation of NHC ligands for catalysis.