The very recent success of Xie et al. (Nat. Commun., 2017, 8, 14827) in achieving the Ir-catalyzed direct borylation of the cage B(3,6)–H of o-carboranes with excellent yield and regioselectivity represents an exciting development in the regioselective functionalization of carboranes. In the present work, the possible catalytic mechanisms and ultimate origin of regioselectivity were studied in detail by using the DFT method. The computational results show that the Ir^III species should be the actual catalyst, rather than the Ir^I compound as supposed from the experiments. Every borylation cycle occurs via two successive oxidative addition–reductive elimination (OxA–ReE) processes, including an unusual Ir^V species in each process. The regioselectivity is determined in the first OxA step of each borylation. Two reaction conformations were calculated and concluded to be competitive. Different distributions of the C–H⋯O hydrogen bonds and B–H⋯O “interactions” were disclosed to be mainly responsible for the different energy profiles of the two reaction conformations. Localized orbital locator (LOL) analysis showed a 26-electron-delocalization structure of the o-carborane, which is considered the fundamental reason for the aromaticity and exceptional chemical stability of this series of carborane (anions). The highly electron-delocalized structure together with the inductive effects of the carbon centers makes the B(3,6)–H sites most electron deficient, resulting in these being the most favorable sites for the OxA reaction to occur with the Ir^III species. This was concluded to be the ultimate origin of the regioselectivity of the title reaction. We believe the present work should be very attractive for experimental scientists since it could be of great help guiding them in the rational design of more efficient catalytic borylation reactions of carboranes with better regioselectivities.

中文翻译：

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Ir催化邻甲碳烷的B（3,6）–H直接硼化的理论研究：实际的催化剂，机理和区域选择性的起源†

谢等人最近的成功。（纳特。COMMUN。，2017年，8，14827）在实现保持架B的铱催化的硼基化直接（3,6）-H的ö具有优良的产率和区域选择性-carboranes表示碳硼烷的区域选择性官能化的令人兴奋的发展。在目前的工作中，使用DFT方法详细研究了可能的催化机理和区域选择性的最终成因。计算结果表明，Ir ^III类物质应该是实际的催化剂，而不是实验中假定的Ir ^I化合物。每个硼酸化周期通过两个连续的氧化加-还原消除（OxA-ReE）过程，每个过程中都包含一个不寻常的Ir ^V物种。在每个硼酸酯化的第一OxA步骤中确定区域选择性。计算了两个反应构象，得出结论是具有竞争性的。据报道，C–H⋯O氢键和B–H⋯O“相互作用”的不同分布主要负责两个反应构象的不同能量分布。局部轨道定位器（LOL）分析显示，o的26电子离域结构-碳硼烷，这被认为是该系列碳硼烷（阴离子）具有芳香性和出色的化学稳定性的根本原因。高电子离域结构以及碳中心的感应效应使B（3,6）–H位点最缺乏电子，从而使它们成为与Ir ^III物种发生OxA反应的最有利位点。结论是标题反应的区域选择性的最终起源。我们认为，目前的工作对实验科学家来说应该是非常有吸引力的，因为它可以极大地帮助他们合理设计具有更好区域选择性的碳硼烷更有效的催化硼化反应。