Calculation of Chemical Shifts. II. The Xenon Fluorides

Xenon chemical shifts in the xenon fluorides XeF2, XeF4, XeF6, and XeOF4 are calculated by means of the general methods presented in I. Comparisons with the experimental chemical shifts show that the change in σ(2), the paramagnetic contribution, is the dominant term and that a localized description using spd hybrid zenon orbitals gives better agreement with experiment than a delocalized MO description using no d hybridization. In addition, the indirect Xe–F and Xe–O coupling constants observed in XeF2, XeF4, and XeOF4 are more consistent with the localized models. The fluorine chemical shifts are used to estimate the ionicity of the Xe–F bonds. Also, a comparison of the anisotropy predicted for the fluorine shift in XeF4 with an experimental value shows that the fluorine shifts result almost entirely from differences in σ(2).