Iridium-Mediated Regioselective B–H/C–H Activation of Carborane Cage: A Facile Synthetic Route to Metallacycles with a Carborane Backbone

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• 作者：Zi-Jian Yao ; Wei-Bin Yu ; Yue-Jian Lin ; Sheng-Li Huang ; Zhen-Hua Li ; Guo-Xin Jin
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：February 19, 2014
• 年：2014
• 卷：136
• 期：7
• 页码：2825-2832
• 全文大小：533K
• ISSN：1520-5126

文摘

One-pot reactions of carborane carboxylic acids (L), [Cp*IrCl₂]₂, and silver salt are reported, which lead to regioselective B鈥揌 or C鈥揌 bond activation at ambient temperature in good yields. This process is demonstrated for three carborane (o-, m-, p-) dicarboxylates, and metal-mediated B鈥揌 functionalization of a p-carborane derivative is accomplished for the first time. Two metal-induced self-assembly routes to tetra-nuclear metallacycles 3 and 5 were performed through B(4, 7)/H and B(2, 10)/H activation, respectively, and the two metallacycles were found to be stable and to exist in solution as discrete complexes. Different activation modes in the carborane cage were ascribed to the characteristic structure of the products and the electronic density differences. The analogous reaction of o-carborane monocarboxylate with the same metal precursor gave the C鈥揌 activation complex 6, indicating that the B鈥揌 bond is more stable than the C鈥揌 bond in this carborane cage. The selective activation was confirmed by DFT calculation results. In this study, a facile and efficient synthetic route has been developed through specific B鈥揌 bond activation to construct carborane-based metallacycles that are unavailable by conventional methods.