Characterization of NMR Deshielding in Phosphole and the Phospholide Ion

Chesnut, D. B.; Quin, Louis D.

doi:10.1021/ja00100a031

Cited by 68 publications

(52 citation statements)

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“…ADF uses MOs that are generated from linear combinations of fragment orbitals (FOs) (108) to parameterize the electron density, according to Kohn and Sham (109), which is then used to calculate the total electronic energy. Using the calculated energy, the magnetic shielding is determined as described in Appendix B, and the total paramagnetic shielding contribution, s :: p , is arbitrarily decomposed into The contributions to paramagnetic shielding have been analysed according to pair-wise MO mixing several times before, although the analysis was often performed using approximate or empirical methods (110,111), qualitative discussions (40,(112)(113)(114)(115), or schematised representations of the MOs (116)(117)(118). More thorough treatments have tended to account for observed isotropic chemical shift values (39,119); however, relatively few (compared with the total number of accounts of observed/calculated CS) can be found where this discussion is extended to include anisotropic CS (38,41,43,48,120,121).…”

Section: Ramsey's Equations and Modern Computational Softwarementioning

confidence: 99%

Understanding chemical shielding tensors using group theory, MO analysis, and modern density‐functional theory

Widdifield¹,

Schurko²

2009

Concepts Magnetic Resonance

118

177

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In this article, the relationships between molecular symmetry, molecular electronic structure, and chemical shielding (CS) tensors are discussed. First, a brief background on the CS interaction and CS tensors is given. Then, the visualization of the three-dimensional nature of CS is described. A simple method for examining the relationship between molecular orbitals (MOs) and CS tensors, using point groups and direct products of irreducible representations of MOs and rotational operators, is outlined. A number of specific examples are discussed, involving CS tensors of different nuclei in molecules of different symmetries, including ethene (D 2h ), hydrogen fluoride (C 1v ), trifluorophosphine (C 3v ), and water (C 2v ). Finally, we review the application of this method to CS tensors in several interesting cases previously discussed in the literature, including acetylene (D 1h ), the PtX 4 2À series of compounds (D 4h ) and the decamethylaluminocenium cation (D 5d ).

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Section: Ramsey's Equations and Modern Computational Softwarementioning

confidence: 99%

Understanding chemical shielding tensors using group theory, MO analysis, and modern density‐functional theory

Widdifield¹,

Schurko²

2009

Concepts Magnetic Resonance

118

177

View full text Add to dashboard Cite

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“…This trend has been explained in terms of a coupling between the phosphorus lone pair(s) and the ring p electrons. [218] The lowfield shift increases with the number of phosphorus atoms. For [P 5 ]…”

Section: Aromatic Systemsmentioning

confidence: 99%

Phospha‐Organic Chemistry: Panorama and Perspectives

2003

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Since the beginning of the seventies, organophosphorus chemistry has been completely rejuvenated by the discovery of stable derivatives in which phosphorus has the coordination numbers one or two. The chemistry of these compounds mimics the chemistry of their all-carbon analogues. In this Review article this analogy is discussed for the phosphorus counterparts of alkenes, alkynes, and carbenes. In each case, the synthesis, reactivity, and coordination modes are briefly examined. Some special electronic configurations are also discussed, which include one-electron Pbond;P bonds, strained bonds, and aromatic systems. To conclude, some potential applications of this chemistry in the areas of molecular materials and homogeneous catalysis are presented.

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“…3 A semi-quantitative explanation of the nuclear shielding variation can sometimes be provided by the orbital energy and nuclear magnetic shielding tensor analysis. 21,30 The solid-state NMR investigation 55 gave the 11 axis of the 31 P chemical shielding tensor in the diphosphene R-P P-R directed approximately perpendicular to the phosphorus lone pair. This suggested that the 31 P resonance occurred at significantly higher frequency than that of the 13 C nuclei in analogous alkenes, owing to the low-lying n-Ł transition.…”

Section: Molecular Orbital Analysismentioning

confidence: 99%

“…13,20 -32 In particular, NMR shielding calculations were performed for some compounds with formally two-coordinated phosphorus (III). Thus, the GIAO-calculated 31 P chemical shift values were used for the assignment of the 31 P NMR signal of the short-lived Ar-O-P O (Ar 2,6-di-t-Bu-4-Me-C 6 H 2 30 and to explain the observed 31 P chemical shift values for phospholide ions. 31 The IGLO-calculated chemical shift values, the principal values of phosphorus chemical shifts and the orientation of the principal axes of the shielding tensors were analysed for some phosphaalkenes H 2 C P-X (X Ph, 2,5-dimethylphenyl, Cl).…”

Section: Introductionmentioning

confidence: 99%