A comparative quantum chemical investigation of the bonding in first and second row ylides
A comparative quantum chemical investigation of the bonding in first and second row ylides
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第一行叶立德和第二行叶立德成键的比较量子化学研究
DOI：
10.1021/ja00459a017
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发表时间：
1977
影响因子：
15
通讯作者：
S. Wolfe
中科院分区：
文献类型：
--
作者：
F. Bernardi;H. Schlegel;M. Whangbo;S. Wolfe
本文对模型叶立德”TH_3CH ~（2-），+NH_3CH ~（2-），+SH_2CH ~（2-），+OH_2CH ~（2-）“进行了从头算SCF-MO计算（4- 31 G）。在第一行铵和氧鎓叶立德中，+ X-C_键比这些叶立德的稳定互变异构体甲胺和甲醇的XC键长。在第二行叶立德中，+ XC~键比互变异构体甲基膦和甲硫醇的XC键短。第二行叶立德的碳负离子中心比相应的第一行叶立德的碳负离子中心更平坦，更灵活。电荷分布和重叠布居的研究表明，就共价和离子性质而言，第二列叶立德的+ XC~键比相应的第一列叶立德的强。这些不同的发现与实验数据一致，这些都是可用的。第一和第二列叶立德的不同结构特征可以通过基团轨道相互作用图来合理化，该图着重于碳孤对和 * XH n基团轨道之间的稳定和不稳定相互作用。1955年，Doering和Hoffmann 2发表了对四甲基铵、四甲基鏻和三甲基锍阳离子的甲基质子的氘氧化物催化氢-氘交换的动力学研究结果。由于这些反应是通过“鎓”叶立德中间体进行的，因此本工作的目的是以速率常数和活化参数的形式获得有关铵（N+）、磷（P+）和锍（S+）基团稳定（或去稳定）相邻碳负离子中心的不同能力的信息。结果表明，N+、P+和S+交换的活化能分别为32.2、25.6和22.4kcal/mol。这部作品从此成为同类作品中的经典之作，它是
Ab initio SCF-MO computations (4-31G) havebeen performed on the model ylides" THsCH^,+ NH3CH2~,+ SH2CH2~, and+ OH2CH2~. In the first row ammonium and oxonium ylides, the+ X-C_ bonds are longer than the XC bonds of the stable tautomers of these ylides, methylamine and methanol. In the second row ylides, the+ XC~ bonds are short-er than the XC bonds of the tautomers methylphosphine and methanethiol. The carbanionic centers of the second row ylides are more planar and more flexible than those of the corresponding first row ylides. Examinationof charge distributions and overlap populations reveals that, in terms of both their covalentand ionic character, the+ XC~ bonds of the second row ylides are stronger than those of the corresponding first row ylides. These various findings are in agreement with experimental data, where these are available. The different structural characteristics of first and second row ylides can be rationalized interms of group orbital interaction diagrams, whichfocus upon the stabilizing and destabilizing interactions between a carbon lone pair and and* XH „group orbitals. The destabilizing interaction dominates when X is a first row atom, and the stabilizing interaction dominates when X is a second row atom.In 1955, Doering and Hoffmann2 presented the results of a kinetic study of deuterioxide-catalyzed hydrogen-deuterium exchange of the methyl protons of tetramethylammonium, tetramethylphosphonium, and trimethylsulfonium cations. Since these reactions proceed via “onium” ylide inter-mediates, the objective of the work was to obtaininformation, in the form of rate constants and activation parameters, con-cerning the differing abilities of ammonium (N+), phospho-nium (P+), and sulfonium (S+) groups to stabilize (or desta-bilize) a developing adjacent carbanionic center. It was found that the enthalpies of activation were 32.2, 25.6, and 22.4 kcal/mol for the exchange of N+, P+, and S+, respectively. This work has since become a classic of its kind, and it is