THEORETICAL-STUDY ON METAL NMR CHEMICAL-SHIFTS - ELECTRONIC MECHANISMOF THE XE CHEMICAL-SHIFT

The Xe-129 chemical shifts of the complexes XeF2n, XeF2n-1+ and XeOnF6 -2n (n = 1-3) are studied theoretically by ab initio finite perturbati on method. The first-order higher basis functions (FOBFs) are added to the standard basis set for removing the gauge-dependence. The calcula ted values of the Xe chemical shifts agree reasonably with the experim ental values. Though the electronic configuration of Xe is the closed shell 5s(2)5p(6), the electronic mechanism of the Xe chemical shift is shown to be the p-mechanism. Namely, the dominant term in the Xe chem ical shift is the paramagnetic term and it is mainly governed by the X e valence p AO contribution. Actually, as expected, the Xe chemical sh ifts show the U-shaped dependence on the number of the Xe valence p el ectrons. The diamagnetic term is small and depends linearly on the num ber of the ligands.