Coulomb repulsion in multiply charged ions (MCIs) is mitigated by long-range electrostatic interaction with the distant charge separation and delocalized systems. Meanwhile, MCIs featuring the charged centers located at two directly connected atoms (E+/−–E+/−) bear a strong repulsive force, which leads to electron detachment or molecular fragmentation, namely, Coulomb explosion. Here, we describe the synthesis of a trianionic triangular triboron species (B3R63−) through the reductive dealumination from a Cp∗AlB3R6 anion (Cp∗, 1,2,3,4,5-pentamethylcyclopentadienyl). X-ray crystallographic and spectroscopic analyses with the aid of quantum chemical calculations reveal that despite the triply negatively charged skeleton, the B3 core is tightly held by electron-precise B–B bonds, overcoming Coulomb repulsion. In contrast to the extant electron-deficient triborate rings, this molecule exhibits reducing ability and nucleophilicity; thus, it undergoes not only electron transfer but also cyclization and salt metathesis reactions, demonstrating its trait as elusive (R2B−) and ([R2B]22−) surrogates.

中文翻译：

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结晶三阴离子三角硼种类


多电荷离子 （MCI） 中的库仑排斥通过与远距离电荷分离和离域系统的长距离静电相互作用来减轻。同时，具有位于两个直接连接的原子 （E+/−–E+/−） 的带电中心的 MCI 具有很强的排斥力，导致电子分离或分子碎裂，即库仑爆炸。在这里，我们描述了通过 Cp∗AlB3R6 阴离子（Cp∗，1,2,3,4,5-五甲基环戊二烯基）的还原脱离合成三离子三角硼物质 （B3R63−）。借助量子化学计算的 X 射线晶体学和光谱分析表明，尽管骨架带三重负电荷，但 B3 核心被电子精确的 B-B 键紧紧抓住，克服了库仑排斥。与现存的缺电子 triborate 环相比，该分子表现出还原能力和亲核性;因此，它不仅经历电子转移，还经历环化和盐复分解反应，证明其作为难以捉摸的 （R2B−） 和 （[R2B]22−） 替代物的特性。