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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Stretching the P-C Bond. Variations on Carbenes and Phosphanes
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Stretching the P-C Bond. Variations on Carbenes and Phosphanes

机译：拉伸P-C键。 碳酸盐和磷的变化

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摘要

The stability and the structure of adducts formed between four substituted phosphanes (PX3, X:H, F, Cl, and NMe2) and 11 different carbenes have been investigated by DFT calculations. In most cases, the structure of the adducts depends strongly on the stability of the carbene itself, exhibiting a linear correlation with the increasing dissociation energy of the adduct. Carbenes of low stability form phosphorus ylides (F), which can be described as phosphane -> carbene adducts supported with some back-bonding. The most stable carbenes, which have high energy lone pair, do not form stable F-type structures but carbene -> phosphane adducts (E-type structure), utilizing the low-lying lowest unoccupied molecular orbital (LUMO) of the phosphane (with electronegative substituents), benefiting also from the carbene-pnictogen interaction. Especially noteworthy is the case of PCl3, which has an extremely low energy LUMO in its T-shaped form. Although this PCl3 structure is a transition state of rather high energy, the large stabilization energy of the complex makes this carbene-phosphane adduct stable. Most interestingly, in case of carbenes with medium stability both F- and E-type structures could be optimized, giving rise to bond-stretch isomerism. Likewise, for phosphorus ylides (F), the stability of the adducts G formed from carbenes with hypovalent phosphorus (PX-phosphinidene) is in a linear relationship with the stabilization of the carbene. Adducts of carbenes with hypervalent phosphorus (PX5) are the most stable when X is electronegative, and the carbene is highly nucleophilic.
机译：通过DFT计算研究了四种取代磷（PX3，X：H，F，Cl和NME2）和11种不同碳酸之间形成的加合物的稳定性和结构。在大多数情况下，加合物的结构在强烈地取决于卡贝蛋白本身的稳定性，表现出与加合物的增加的解离能的线性相关性。低稳定性磷酰胺（F）的碳纤维（F），其可描述为磷酸盐 - >用一些后粘合负载的卡宾固定剂。具有高能量孤牌对的最稳定的碳酸盐，不形成稳定的F型结构，而是脱羧 - >磷酸磷酸盐（E型结构），利用磷酸的低位最低未占用的分子轨道（LumO）（与电负代取代物），也是来自卡宾 - 肺植物相互作用的受益。特别值得注意的是PCL3的情况，其在其T形形式具有极低的能量亮度。虽然该PCL3结构是相当高能量的过渡状态，但复合物的大稳定能量使得该碳氮膦加合物稳定。最有趣的是，在具有中等稳定性的碳酸盐的情况下，可以优化F-和E型结构，产生粘合拉伸异构。同样，对于磷酰胺（F），用碳酸（Px-膦烯）形成的加合物G的稳定性是与卡贝稳定的线性关系。当X是电负时，具有高效磷（PX5）的碳糖的加合物是最稳定的，并且卡贝尔是高亲核的。

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