Electrochemical Oxidation of [1-X-12-I-CB 11 Me 10 – ] Anions: Formation of Borenium Ylides [12-Dehydro-1-X-CB 11 Me 10 ] and Iodonium Ylide Anions [{12-(1-X-CB 11 Me 10 – )} 2 I + ]
Electrochemical Oxidation of [1-X-12-I-CB 11 Me 10 – ] Anions: Formation of Borenium Ylides [12-Dehydro-1-X-CB 11 Me 10 ] and Iodonium Ylide Anions [{12-(1-X-CB 11 Me 10 – )} 2 I + ]
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[1-X-12-I-CB 11 Me 10 – ]阴离子的电化学氧化：形成硼叶立德[12-DeHydrogen-1-X-CB 11 Me 10 ]和碘鎓叶立德阴离子[{12-(1
DOI：
10.1021/acs.inorgchem.6b02128
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发表时间：
2016
影响因子：
4.6
通讯作者：
Ludvík, Jiří
中科院分区：
文献类型：
--
作者：
Wahab, Abdul;Kaleta, Jiří;Wen, Jin;Valášek, Michal;Polášek, Miroslav;Michl, Josef;Ludvík, Jiří
12-碘化二十面体碳硼烷阴离子[1-X-12-I-CB11Me10-](X=H，CH3，C2H5，C3H7，C4H9，C6H13和COOCH3)在液态SO2中的循环伏安图显示在铂电极上有两个单电子的阳极氧化峰。奇怪的是，第一个是不可逆转的，第二个是部分可逆的。[1-H-12-I-CB11Me11-]与其与[Et3Si-H-SiEt3]+和/或Et3Si+反应的主要阴离子产物的质谱图表明，它是碘叶立德阴离子[{12-(1-H-CB11Me10-)}2I+]。其可逆氧化为中性叶立德自由基[{12-(1-H-CB11Me10·)}{12-(1-H-CB11Me10-)}I+]是第二个峰。密度泛函几何优化表明，叶立德阴离子和叶立德自由基都非常拥挤，具有异常大的C-I-C价角∼132°；它们是第一批将两个巨大的高度甲基化的CB11笼子连接到同一个原子上的化合物。分子碘是电解的另一种产物。我们提出了一种电极机理，即[1-X-12-I-CB11Me10-]的初始单电子氧化后，碘原子从B-I键转移到SO2，生成弱结合的自由基ISO2·，该自由基不成比例地生成SO2和I2。另一种产物是叶立德[12-脱氢-1-X-CB11Me10]，它在第12位有一个强Lewis酸性的裸露顶点，可以快速地与另一个[1-X-12-I-CB11Me10-]阴离子加成，形成稳定的叶立德阴离子[{12-(1-X-CB11Me10-)}2I+]。在乙腈中，它可能以溶剂加合物的形式存在，[12-dedro-1-X-CB11Me10]已被水捕获，并在很小程度上与甲醇捕获，但不与其他几种潜在的捕捉剂捕获。
Cyclic voltammograms of 12-iodinated icosahedral carborane anions [1-X-12-I-CB11Me10–] (X = H, CH3, C2H5, C3H7, C4H9, C6H13, and COOCH3) show two one-electron anodic oxidation peaks at the Pt electrode in liquid SO2. Oddly, the first is irreversible and the second partially reversible. Mass spectrometry of the principal anionic product of preparative anodic oxidation of [1-H-12-I-CB11Me11–], identical with the anionic product of its reaction with [Et3Si–H–SiEt3]+and/or Et3Si+, allows it to be identified as the iodonium ylide anion [{12-(1-H-CB11Me10–)}2I+]. Its reversible oxidation to a neutral ylide radical [{12-(1-H-CB11Me10•)}{12-(1-H-CB11Me10–)}I+] is responsible for the second peak. A DFT geometry optimization suggests that both the ylide anion and the ylide radical are very crowded and have an unusually large C–I–C valence angle of ∼132°; they are the first compounds with two bulky highly methylated CB11cages attached to the same atom. Molecular iodine is another product of the electrolysis. We propose an electrode mechanism in which initial one-electron oxidation of [1-X-12-I-CB11Me10–] is followed by a transfer of an iodine atom from the B–I bond to SO2to yield a weakly bound radical ISO2•which disproportionates into SO2and I2. The other product is the borenium ylide [12-dehydro-1-X-CB11Me10], which has a strongly Lewis acidic naked vertex in position 12 that rapidly adds to another [1-X-12-I-CB11Me10–] anion to form the observed stable ylide anion [{12-(1-X-CB11Me10–)}2I+]. In acetonitrile, where it presumably exists as a solvent adduct, [12-dehydro-1-X-CB11Me10] has been trapped with H2O and, to a small extent, with MeOH, but not with several other potential trapping agents.