In free-radical halogenation of aromatics, singly charged ions are usually formed as intermediates. These stable species can be easily observed by time-of-flight mass spectrometry (TOF-MS). Here we used electron and proton beams to ionize chlorobenzene (C6H5Cl) and investigate the ions stability by TOF-MS. Additionally to the singly charged parent ion and its fragments, we find a significant yield of doubly and triply charged parent ions not previously reported. In order to characterize these species, we used high-level theoretical methods based on density functional theory (DFT), coupled-cluster (CC), and generalized valence bond (GVB) to calculate the structure, relative stabilities, and bonding of these dications and trications. The most stable isomers exhibit unusual carbon-chlorine multiple bonding: a terminal C═Cl double bond in a formyl-like CHCl moiety (1, rC-Cl = 1.621 Å) and a ketene-like C═C═Cl cumulated species (2, rC-Cl = 1.542 Å). The calculations suggest that an excited state of 2 has a nitrile-like C≡Cl triple bond structure.

中文翻译：

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由氯苯形成的双电荷和三电荷物种揭示了不寻常的 C-Cl 多重键

在芳烃的自由基卤化中，通常形成单电荷离子作为中间体。这些稳定的物质可以通过飞行时间质谱 (TOF-MS) 轻松观察到。在这里，我们使用电子束和质子束来电离氯苯 (C6H5Cl)，并通过 TOF-MS 研究离子稳定性。除了单电荷母离子及其碎片之外，我们还发现了以前未报道过的双电荷和三电荷母离子的显着产量。为了表征这些物种，我们使用基于密度泛函理论 (DFT)、耦合簇 (CC) 和广义价键 (GVB) 的高级理论方法来计算这些指示的结构、相对稳定性和键合和麻烦。最稳定的异构体表现出不寻常的碳-氯多重键合：甲酰基样 CHCl 部分中的末端 C=Cl 双键 (1, rC-Cl = 1.621 Å) 和烯酮样 C=C=Cl 累积物质 (2, rC-Cl = 1.542 Å)。计算表明，激发态 2 具有类似腈的 C≡Cl 三键结构。