Ab initio coupled Hartree–Fock perturbation theory (CHFPT) calculations on PF3, PF<sup> + </sup><sub>4</sub> , PF5, PF<sup> - </sup><sub>6</sub>, and PO<sup>3 - </sup><sub>4</sub> using large polarized Gaussian bases satisfactorily reproduce observed 31P NMR chemical shifts. In PF3 the 31P NMR shielding constant sigma increases as the P–F bond distance or the F–P–F angle is decreased. The 31P chemical shift delta of PF<sup> + </sup><sub>4</sub> is predicted to be ~−15 ppm (vs 85% H3PO4). Although the average values of the isotropic NMR shieldings are overestimated by the calculations (e.g., sigma<sup>P</sup><sub>av</sub> calc. 372.5 ppm vs expt. 259±20 ppm in PF3) the anisotropy in sigmaP is well reproduced (calc. 244.7 ppm vs expt. 228±2 ppm). The ~200 ppm smaller 31P NMR shielding of PF3 compared to PF5 arises partly from a diamagnetic contribution lower by ~100 ppm and partly from the more negative paramagnetic contribution arising from mixing of the 8a1 P lone pair MO with unoccupied orbitals of e symmetry in PF3.

Coupled Hartree-Fock calculations of 31P NMR shieldings in phosphorous fluorides and PO_4^{3-} / J. A., Tossell; Lazzeretti, Paolo. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - STAMPA. - 86:(1987), pp. 4066-4069.

Coupled Hartree-Fock calculations of 31P NMR shieldings in phosphorous fluorides and PO_4^{3-}

LAZZERETTI, Paolo
1987

Abstract

Ab initio coupled Hartree–Fock perturbation theory (CHFPT) calculations on PF3, PF + 4 , PF5, PF - 6, and PO3 - 4 using large polarized Gaussian bases satisfactorily reproduce observed 31P NMR chemical shifts. In PF3 the 31P NMR shielding constant sigma increases as the P–F bond distance or the F–P–F angle is decreased. The 31P chemical shift delta of PF + 4 is predicted to be ~−15 ppm (vs 85% H3PO4). Although the average values of the isotropic NMR shieldings are overestimated by the calculations (e.g., sigmaPav calc. 372.5 ppm vs expt. 259±20 ppm in PF3) the anisotropy in sigmaP is well reproduced (calc. 244.7 ppm vs expt. 228±2 ppm). The ~200 ppm smaller 31P NMR shielding of PF3 compared to PF5 arises partly from a diamagnetic contribution lower by ~100 ppm and partly from the more negative paramagnetic contribution arising from mixing of the 8a1 P lone pair MO with unoccupied orbitals of e symmetry in PF3.
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4069
Coupled Hartree-Fock calculations of 31P NMR shieldings in phosphorous fluorides and PO_4^{3-} / J. A., Tossell; Lazzeretti, Paolo. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - STAMPA. - 86:(1987), pp. 4066-4069.
J. A., Tossell; Lazzeretti, Paolo
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11380/454568
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