Ab initio calculation of the 31P NMR shielding tensor for the series PO aF b−(2 a+ b−5) , a+ b=4 and for HPO 42−

Abstract

Ab initio coupled Hartree-Fock perturbation theory (CHFPT) calculations on PO 4 3−, PO 3F 2−, PO 2F 2 −, PF 3O, PF 4 + and HPO 4 2− using large polarized Gaussian bases satisfactorily reproduce experimental trends in 31P magnetic shielding anisotropies.Accurate evaluation of the shielding tensor for HPO 4 2− requires the inclusion of the H atom. Along the series PO a F b −(2 a+ b−5) the calculated isotropic shielding shows a “sagging” pattern, i.e. the shielding is smallest for the intermediate member of the series PO 3F 2−. The shielding for this species is, however, a strong function of the P-F and P-O distances. PO 3F 2− and HPO 4 2− are calculated to be similar in both average shielding and shielding anisotropy.