Penner G H, Power W P, Curtis R D, Wasylishen R E
Department of Chemistry, Dalhousie University, Halifax, N.S., Canada.
Solid State Nucl Magn Reson. 1992 Jun;1(2):85-91. doi: 10.1016/0926-2040(92)90020-a.
Phosphorus-31 powder NMR spectra and high-resolution MAS spectra have been obtained for a number of stabilized phosphorus ylids under conditions of high-power proton decoupling and cross-polarization. The 31P CP/MAS spectra are compared to those obtained from isotropic solutions. The variation of chemical shift anisotropy and of the principal components of the 31P chemical shift tensor determined from 31P powder NMR line shapes are discussed in terms of the relative importance of accepted valence bond resonance structures. The results indicate that the invariance of the isotropic chemical shift, delta iso, observed in previous 31P NMR investigations of phosphorus ylids in solution is due to fortuitous cancellation of opposing changes in the principal components, delta 11 and delta 33, of the 31P chemical shift tensor. The 31P dipolar NMR powder spectrum of a typical stabilized ylid, (C6H5)3(31)P-13CHC(O)OCH2CH3, is analyzed in order to obtain the orientation of the 31P chemical shift tensor with respect to the 31P-13C alpha dipolar vector.
在高功率质子去耦和交叉极化条件下，已获得了多种稳定磷叶立德的磷-31粉末核磁共振谱和高分辨率魔角旋转谱。将31P CP/MAS谱与从各向同性溶液中获得的谱进行了比较。根据公认的价键共振结构的相对重要性，讨论了由31P粉末核磁共振线形确定的化学位移各向异性和31P化学位移张量主分量的变化。结果表明，在先前对溶液中磷叶立德的31P NMR研究中观察到的各向同性化学位移δiso的不变性，是由于31P化学位移张量主分量δ11和δ33中相反变化的偶然抵消。分析了典型稳定叶立德(C6H5)3(31)P-13CHC(O)OCH2CH3的31P偶极核磁共振粉末谱，以获得31P化学位移张量相对于31P-13Cα偶极矢量的取向。
