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

The effects of intramolecular and intermolecular coordination on 31 P 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 31 P nuclear shielding amounting to approximately 150 ppm on changing the phosphorous coordination number by one. A major importance of solvent effects on 31 P 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 31 P NMR chemical shifts, provided relativistic corrections are taken into account, the latter being of crucial importance in the description of 31 P nuclear shielding. Copyright © 2012 John Wiley & Sons, Ltd.