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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >An intramolecular ortho-assisted activation of the silicon-hydrogen bond in arylsilanes: an experimental and theoretical study
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An intramolecular ortho-assisted activation of the silicon-hydrogen bond in arylsilanes: an experimental and theoretical study

机译：芳基硅烷中硅 - 氢键的分子内邻 - 辅助激活：实验和理论研究

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摘要

An intramolecular activation of the Si-H bond in arylsilanes by selected ortho-assisting functional groups based on boron, carbon and phosphorus was investigated experimentally and by means of theoretical calculations. The major conclusion drawn is that the presence of a negatively charged oxygen atom in the functional group is essential for providing effective chelation to the silicon atom which in turn results in the increased hydridic character of a resulting five-coordinated species. In contrast, an intermolecular attack of hydroxide on the silicon atom in aryldimethylsilane results in the activation of the silicon-aryl bond. This increased reactivity of the Si-H bond in intramolecularly coordinated arylsilanes can be ascribed to a significant trans effect which operates in the preferred configuration. Hydrolytic cleavage of the Si-H bond results in dihydrogen elimination and the formation of various silicon heterocyclic systems such as benzosiloxaboroles, spiro-bis(siloxa) borinate, benzosilalactone and benzophosphoxasilole. In addition, intermolecular reduction of benzaldehydes with ortho-boronated arylsilane was observed whereas compounds bearing other reducible functional groups (COMe, COOEt, CN and NO2) were inert under comparable conditions. Specifically, an intramolecular reduction of the CN group in an ortho-silylated benzonitrile derivative was observed. The mechanism of Si-H bond activation was investigated by the DFT theoretical calculations. The calculations showed that the intramolecular coordination of the silicon atom effectively prevents the cleavage of the Si-aryl bond. Furthermore, the reaction is favored in anionic systems bearing COO-, B(OH)(3) -or CH2O-groups, while in the case of neutral functional groups such as PO(OEt)(2) the process is much slower.
机译：在通过基于硼，碳和磷中的邻位协助官能团芳基硅烷的Si-H键的分子内活化进行了实验，并通过理论计算的方法研究。得出的主要结论是带负电荷的氧原子的官能团的存在是在硅原子上，其在又导致增加所得到的五配位物质的氢负离子字符提供有效的螯合是必不可少的。与此相反，氢对硅 - 芳基键的激活aryldimethylsilane结果硅原子的分子间攻击。这种增加在分子内配位芳基硅烷的Si-H键的反应性可以归因于工作在该优选结构的显著反效果。在消除二氢中的Si-H键的结果水解裂解和各种硅杂环体系的形成如benzosiloxaboroles，螺双（siloxa）borinate，benzosilalactone和benzophosphoxasilole。此外，观察到，而轴承其他可还原官能团化合物与邻 - 硼化芳基硅烷苯甲醛的分子间还原（COME，COOEt烷基，CN和NO 2）为惰性的相当条件下。具体地，观察到CN基团的邻 - 甲硅烷基化苄脒衍生物的分子内还原。的Si-H键活化的机理是由DFT理论计算的影响。计算表明，在硅原子的分子内配位有效地防止硅 - 芳基键的裂解。此外，反应是有利的在阴离子体系轴承COO - ，B（OH）（3） - 或CH 2 O的基团，而在中性官能团，如PO（OET）的情况下，（2）该方法是慢得多。

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