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首页> 外文期刊>Chemistry: A European journal >On the p-coordinating limit of NHC-phosphenium cations toward rh ~icenters
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On the p-coordinating limit of NHC-phosphenium cations toward rh ~icenters

机译：NHC-phosph阳离子对r中心的p配位极限

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摘要

Two types of imidazoliophosphane with additional electron-withdrawing substituents, such as alkoxy or imidazolio groups, are experimentally described and theoretically studied. Diethyl N,N'-2,4,6-methyl(phenyl) imidazoliophosphonite is shown to retain a P-coordinating ability toward a {RhCl(cod)} (cod=cycloocta-1,5-diene) center, thus competing with the cleavage of the labile C-P bond. Derivatives of N,N'-phenylene-bridged diimidazolylphenylphosphane were isolated in good yield. Whereas the dicationic phosphane proved to be inert in the presence of [{RhCl(cod)}2], the monocationic counterpart was shown to retain the P-coordinating ability toward a {RhCl(cod)} center, thus competing with the N-coordinating ability of the nonmethylated imidazolyl substituent. The ethyl phosphinite version of the dication, thus possessing an extremely electron-poor PIII center, was also characterized. According to the difference between the calculated hemolytic and heterolytic dissociation energies, the N _2C P bond of imidazoliophosphanes with aryl, amino, or alkoxy substituents on the P atom is shown to be of dative nature. The P-coordinating properties of imidazoliophosphanes with various combinations of phenyl or ethoxy substituents on the P atom and those of six diimidazolophosphane derivatives with zero, one, or two methylium substituents on the N atom, were analyzed by comparison of the corresponding HOMOs and LUMOs and by calculation of the IR C=O stretching frequencies of their [RhCl(CO) _2] complexes. Comparison of the n CO values allows the family of the electron-poor Im +PRR' (Im=imidazolyl) potential ligands to be ranked in the following order versus (R,R'): P(OEt) _3< (Ph,Ph)<(Ph,OEt)<(OEt,OEt)< PF _3<(Ph,Im)<(Ph,Im ~+)<(OEt,Im ~+). The (Ph,Im) representative is therefore the least electron-donating phosphane for which coordinating behavior toward a RhI center has been experimentally evidenced to date. Ultimate applications in catalysis could be envisaged.
机译：通过实验描述和理论研究了具有额外的吸电子取代基的两种类型的咪唑并碘膦，例如烷氧基或咪唑并基。 N，N'-2,4,6-甲基（苯基）咪唑啉亚膦酸二乙酯显示出对{RhCl（cod）}（cod = cycloocta-1,5-diene）中心保持P配位能力，因此与不稳定的CP键的裂解。以良好的产率分离出N，N′-亚苯基桥接的二咪唑基苯基膦的衍生物。尽管在[{RhCl（cod）} 2]存在下，二价膦被证明是惰性的，但单阳离子对应物却显示出对{RhCl（cod）}中心的P配位能力，从而与N-竞争。非甲基化的咪唑基取代基的配位能力。还表征了该指示剂的乙基次膦酸酯版本，因此具有极差的PIII电子中心。根据计算的溶血和溶血解离能之间的差异，显示咪唑并膦原子在P原子上具有芳基，氨基或烷氧基取代基的N _2C P键具有导数性质。通过比较相应的HOMO和LUMO，比较了P原子上具有苯基或乙氧基取代基的各种组合的咪唑并膦与N原子上具有零，一个或两个甲基取代基的六个二咪唑并膦衍生物的P配位性能。通过计算其[RhCl（CO）_2]配合物的IR C = O拉伸频率。通过比较n个CO值，可以将相对于（R，R'）的电子贫化Im + PRR'（Im =咪唑基）潜在配体族按以下顺序排列：P（OEt）_3 <（Ph，Ph ）<（Ph，OEt）<（OEt，OEt）

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