Electron-coupled nuclear spin–spin interactions in cubic PbF2 and the 19F chemical shift

The 19F NMR multipulse spectrum of a single crystal of cubic PbF2 was found to vary with the orientation of the crystal in the static magnetic field. This enabled the isotropic J and anisotropic (or pseudodipolar) J′ electron-coupled spin–spin interactions to be determined. J is ±2.15±0.05 kHz with the negative sign being most likely according to the theory of Jameson and Gutowsky. J′ is found to be negative with a magnitude 0.07±0.05 kHz or 2.71±0.05 kHz, the latter value being consistent with a negative sign for J and with the expectations of simple localized-bond models and the extent of the non-s bonding in cubic PbF2. For J=−2.15 and J′=−2.71 kHz, the spin–spin coupling anisotropy is +5.42±0.2 kHz. The 19F chemical shift of cubic PbF2 is −127.7±0.5 ppm at room temperature, with respect to C6F6. This shift fits the correlation of isotropic chemical shifts with cation radii previously established for the group IIa difluorides.