Factors favoring an M...H-C interaction in metal-methyl complexes. An MO analysis
Factors favoring an M...H-C interaction in metal-methyl complexes. An MO analysis
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DOI：
10.1021/ja00291a016
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发表时间：
1985-03
影响因子：
15
通讯作者：
O. Eisenstein;Y. Jean
中科院分区：
文献类型：
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作者：
O. Eisenstein;Y. Jean
我们这项工作的目的并不是试图最终解决与芳香硝化机制相关的争议点，而是提供定量描述并更好地理解可能涉及这些过程的一些系统。因此，我们提出并讨论了与弱结合和强结合的苯-NO2+和甲苯-NO2+络合物的形成相关的结构、原子电荷重新分布和稳定能，这些络合物是这些芳香族分子硝化中可能的中间阶段。在我们的结果中可以看到某些有趣且一致的模式。其中一个事实是，相同类型的共振结构似乎是已研究的四种配合物中每一种的主要贡献者。另一个是甲苯及其络合物中甲基所发挥的两种功能的图片：首先，它引起芳香环内的电荷重排，从而使与其连接的碳变得更加带正电，在每种情况下增量基本上相同。由此产生的静电相互作用可能是甲苯-NO 2+ 络合物中各种稳定作用的原因，这些稳定作用导致了众所周知的CH 3 的邻位、对位导向特性。其次，甲基在NO2强吸电子力的刺激下，是电子电荷的来源，电荷来自其氢。
Our intention in this work has not been to try to conclusively settle the controversial points related to the mechanism of aromatic nitration but ratherto provide quantitative descriptions and a better understanding of some systems that may be involved in these processes. We have accordingly presented anddiscussed the structures, atomic charge redistributions, and stabilization energies associated with the formation of both weakly and strongly bound benzene-N02+ and toluene-N02+ complexes that are possible intermediate stages in the nitration of these aromatic molecules. Certain interesting and consistent patterns can be seen in our results. Oneof these is thefact that the same type of resonance structure appears to be the dominant contributor to each of the four complexes that have been studied. Another is the picture that has emerged of the two functions performed by the methyl group in toluene and its complexes: First, it induces a rear-rangement of charge within the aromatic ring whereby the carbon to which it is attached becomes more positive, by essentially the same increment in each case. The resulting electrostatic interaction, may be responsible for the various stabilization effects in the toluene-N02+ complexes that result in the well-known ortho, para-directing properties of CH3. Second, the methyl group, under the stimulus of the strong electron-attracting power of the N02, is a source of electronic charge, which comes from itshydrogens.