The effects of intramolecular and intermolecular coordination on 31P nuclear shielding: phosphorylated azoles

• Published in: Magnetic resonance in chemistry Vol. 50; no. 2; pp. 120 - 127
• Main Authors: Chernyshev, Kirill A., Larina, Ludmila I., Chirkina, Elena A., Krivdin, Leonid B.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-02-2012
• Subjects: 31P NMR; 31P shielding constants; coordination effects; DFT; GIAO; PCM; pyrazoles; relativistic corrections; spin-orbit interaction; ZORA
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.2854

The effects of intramolecular and intermolecular coordination on 31P nuclear shielding have been investigated in the series of tetracoordinated, pentacoordinated and hexacoordinated N‐vinylpyrazoles and intermolecular complexes of N‐vinylimidazole and 1‐allyl‐3,5‐dimethylpyrazole with phosphorous pentachloride both experimentally and theoretically. It was shown that either intramolecular or intermolecular coordination involving phosphorous results in a dramatic 31P nuclear shielding amounting to approximately 150 ppm on changing the phosphorous coordination number by one. A major importance of solvent effects on 31P nuclear shielding of intramolecular and intermolecular complexes involving N → P coordination bond has been demonstrated. It was found that the zeroth‐order regular approximation–gauge‐including atomic orbital–B1PW91/DZP method was sufficiently accurate for the calculation of 31P NMR chemical shifts, provided relativistic corrections are taken into account, the latter being of crucial importance in the description of 31P nuclear shielding. Copyright © 2012 John Wiley & Sons, Ltd.
The effects of intramolecular and intermolecular coordination on 31P nuclear shielding have been investigated in the series of tetracoordinated, pentacoordinated and hexacoordinated N‐vinylpyrazoles and intermolecular complexes of N‐vinylimidazole and 1‐allyl‐3,5‐dimethylpyrazole with phosphorous pentachloride both experimentally and theoretically. It was shown that either intramolecular or intermolecular coordination involving phosphorous results in a dramatic 31P nuclear shielding amounting to approximately 150 ppm on changing the phosphorous coordination number by one. A major importance of solvent effects on 31P nuclear shielding of intramolecular and intermolecular complexes involving N→P coordination bond has been demonstrated. It was found that the zeroth‐order regular approximation‐gauge‐including atomic orbital‐B1PW91/DZP method was sufficiently accurate for the calculation of 31P NMR chemical shifts, provided relativistic corrections are taken into account, the latter being of crucial importance in the description of 31P nuclear shielding.