Nuclear magnetic resonance of phosphorus compounds. VII. Evidence for steric effects on the phosphorus-31-selenium-77 coupling and phosphorus-31 chemical shifts
Nuclear magnetic resonance of phosphorus compounds. VII. Evidence for steric effects on the phosphorus-31-selenium-77 coupling and phosphorus-31 chemical shifts
复制标题
磷化合物的核磁共振。
DOI：
10.1021/ja00784a087
复制
发表时间：
1973
影响因子：
15
通讯作者：
P. Kroon
中科院分区：
文献类型：
--
作者：
R. Pinnell;C. Megerle;S. L. Manatt;P. Kroon
(1)本系列的前一篇论文：AH Cowley，J. R。Schweiger和S. L. Manatt，Chem. Commun.，1491（1970）。由于pT-dT键与磷有关，我们合成了一些三芳基膦和硒化三芳基膦，并研究了它们的磷核磁共振谱。我们希望报告的证据表明，如何的NMR参数磷的局部电子环境是空间扰动可以偏离那些预期的基础上观察到的取代基效应相关性2在不拥挤的molecular.There是一些实际的困难，值得一提的31 P光谱的三芳基邻菲和三芳基膦硒化物，我们已经研究。直接测定这类化合物的~（31）P化学位移是不容易的，因为芳环上的质子与磷之间广泛的自旋-自旋耦合使磷的核磁共振谱在一个宽的谱带上变模糊。在三芳基膦硒化物中直接观察到的31 P-77 Se偶联（仅7.5%的分子表现出）似乎更难以观察到。此外，这些化合物中的许多具有有限的溶解度，因此增加浓度不是解决信噪比问题的可能方案。然而，利用质子噪声去耦3沿着数字扫描时间平均4和提高探针温度，可以成功测量相关核磁共振参数。典型光谱如图1所示。在对位取代的三苯基膦和
(1) Previous paper in this series: AH Cowley, J. R. Schweiger, and S. L. Manatt, Chem. Commun., 1491 (1970). pT-dT bonding involving phosphorus, we have had occasion to synthesize and study the phosphorus nmr spectra of a number of triarylphosphines and triaryl-phosphine selenides. We wish to report evidence which indicates how the nmr parameters for phosphorus whose local electronic environment is sterically perturbed can deviate from those expected on the basis of observed substituent effect correlations2 in less crowded molecules.There are some practical difficulties which deserve mention regarding the 31P spectra of the triarylphos-phines and triarylphosphine selenides which we have studied. Direct determination of the 31P chemical shifts of these classes of compounds is not easily ac-complished because extensive spin-spin coupling between the protons on the aromatic rings and phosphorus smears the nmr spectrum for the latter over a wide band. The direct observation of the 31P-77Se coupling in the triarylphosphine selenides, which is exhibited by only 7.5% of the molecules, appeared even more difficult to observe. In addition, many of these compounds possess limited solubility so an increase in concentration was not a possible solution to the signal-to-noise prob-lem. However, taking advantage of proton-noise decoupling3 along with digital-sweep time averaging4 and elevated probe temperature, it was possible to make successful measurement of the relevant nmr parameters. Typical spectra are shown in Figure 1. In the para-substituted triphenylphosphines and