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首页> 外文期刊>Chemistry: A European journal >Towards Spontaneous Heterolysis of the Homonuclear P-P Bond in Diphosphines: The Case of Diazaphospholeniumtriphospholides
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Towards Spontaneous Heterolysis of the Homonuclear P-P Bond in Diphosphines: The Case of Diazaphospholeniumtriphospholides

机译：对双膦中同质P-P键的自发异构化：二氮杂磷鎓三磷酸酯的情况

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摘要

Computational studies on a series of polyphospholyl-substituted N-heterocyclic phosphines (CH),(NR), P-P-n(CH)(5-n) (R-Me, n=1-5) disclosed that increasing formal replacement of CH units in the phosphole ring by phosphorus atoms is associated with an increase in P-P distances and charge separation, and a decrease in covalent bond orders. Altogether, these trends imply that the CH versus P substitution enhances ionic P-P bond polarization in these compounds. Experimental verification of this hypothesis was obtained for the triphospholyl diazaphospholenes (CR)(2)(NR')(2)P-P-3-(CtBu)(2) (8a: R=H, R'=tBu: 8b: R=Me, R'=Mesityl [Mes]), which were prepared through metathesis reactions from suitable precursors and identified by solution and solid-state NMR data and a single-crystal X-ray diffraction study of 8a. Analysis of J(PP) coupling patterns suggested that both species are characterized by the absence of a strong covalent P-P bond connecting both rings. This interpretation was confirmed by the finding of a unique P-P distance of 2.79 angstrom For crystalline 8a, and further supported by computational studies, which led to the conclusion that both species are better described as diazophospholenium-triphospolide contact ion pairs rather than covalent molecules. Variable-temperature (VT) NMR spectra of 8b showed a collapse of J(PP) couplings between atoms in different rings, which indicates scrambling of the diazaphospholenium and triphospholide units between different molecules in solution, and further substantiates the proposed view on the molecular structure.
机译：对一系列多羟基取代的N-杂环膦（CH），（NR），PPn（CH）（5-n）（R-Me，n = 1-5）的计算研究表明，增加CH中的CH单元的正式取代磷原子引起的磷环与PP距离增加和电荷分离以及共价键序减少有关。总而言之，这些趋势暗示在这些化合物中CH对P取代增强了离子性P-P键极化。通过对三羟酰基二氮杂膦烯（CR）（2）（NR'）（2）PP-3-（CtBu）（2）（8a：R = H，R'= tBu：8b：R = Me，R'= Mesityl [Mes]），是通过合适的前体通过复分解反应制备的，并通过溶液和固态NMR数据以及8a的单晶X射线衍射研究进行了鉴定。对J（PP）耦合模式的分析表明，这两个物种的特征都是没有连接两个环的强共价P-P键。对于晶体8a的独特的P-P距离为2.79埃的发现证实了这种解释，并得到了计算研究的进一步支持，计算研究得出的结论是，两个物种均被更好地描述为重氮phosph-三磷接触离子对而不是共价分子。 8b的可变温度（VT）NMR光谱显示不同环中原子之间的J（PP）偶合塌陷，这表明溶液中不同分子之间的diazaphospholenium和triphospholide单元发生混乱，并进一步证实了分子结构的建议观点。

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