A monomeric dilithio methandiide with a distorted trans-planar four-coordinate carbon.
A monomeric dilithio methandiide with a distorted trans-planar four-coordinate carbon.
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DOI：
10.1002/anie.201002483
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发表时间：
2010-07
影响因子：
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通讯作者：
Oliver J. Cooper;Ashley J. Wooles;J. McMaster;W. Lewis;A. Blake;S. Liddle
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文献类型：
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作者：
Oliver J. Cooper;Ashley J. Wooles;J. McMaster;W. Lewis;A. Blake;S. Liddle
这种四面体四配位碳的范例多年来一直是绝对的。尽管如此，化学家们一直着迷于这样一个概念，即可能会发现具有平面四配位碳几何结构的化合物（II）。[2]在货车t霍夫提出后的近100年里，平面四配位碳在霍夫曼描述了这种几何结构的理论模型后得到了更认真的考虑，在该模型中，一个sp2杂化的碳与四个取代基（III）形成两个双电子双中心（2 e，2c）键和一个双电子三中心（2 e，3c）键。[3]对于最简单的例子，甲烷，四面体几何形状相对于平面形式更稳定，约为530 kJ molecule 1。[3，4]因此，为了在实验上实现平面四配位碳，已经追求了施加平面四配位几何形状的各种策略，其中，有机金属衍生物已经取得了最显著的进展。[5]对于真正的甲烷，vonSchleyer在理论上[6]和实验上[7]表明，用碱金属顺序取代氢原子会增加平面四配位甲烷的稳定性。此外，对于二取代的甲烷衍生物，例如H2 CLi 2，发现反式平面形式（IV）相对于顺式平面形式（V）被约125 kJ mol-1去稳定化。[6]虽然反式中的线性2 e，3c π轨道
This paradigm of tetrahedral four-coordinate carbon appeared absolute for many years. Nevertheless, chemists have long been fascinated with the concept that compounds exhibiting a planar four-coordinate carbon geometry might be found (II).[2] Nearly a hundred years after van t Hoff s proposal, planar four-coordinate carbon became more seriously considered after Hoffmann described a theoretical model for this geometry in which an sp2-hybridized carbon forms two two-electron-two-center (2e, 2c) bonds and a twoelectron-three-center (2e, 3c) bond to the four substituents (III).[3] For the simplest example, methane, the tetrahedral geometry is more stable relative to the planar form by about 530 kJ molÀ1.[3, 4] Therefore, to experimentally realize planar four-coordinate carbon, various strategies to impose a planar four-coordinate geometry have been pursued, and of these, organometallic derivatives have delivered the most significant advances.[5]For genuine methanes, vonSchleyer showed theoretically [6] and experimentally [7] that the sequential replacement of hydrogen atoms with alkali metals results in an increase in the stabilization of planar four-coordinate methanes. Furthermore, for disubstituted methane derivatives, such as H2CLi2, the trans-planar form (IV) was found to be destabilized by about 125 kJmolÀ1 relative to the cis-planar form (V).[6] Although the linear 2e, 3c π orbital in the trans