Correlation of 31P chemical shift parameters to molecular structures of hexacoordinate organophosphorus compounds in the solid state

Abstract

³¹ P principal elements of chemical shift tensors δ_ii for a series of hexacoordinate organophosphorus compounds have been obtained from spinning sideband intensities employing the MASNMR program based on a graphical method of Berger and Herzfeld. It was found that anisotropy parameters Δδ and span Ω reflect the distortion of the molecular structure from the ideal octahedral geometry. The asymmetry parameter η and skew κ suggest that the phosphorus shielding depends not only on the local bonding, but also on the octahedral structure as a whole. Comparison of isotropic chemical shifts in solution and in solids revealed that in both phases the molecular structures are not changed. Moreover, this work shows that for P^VI moieties with unknown X-ray structure, crucial information regarding the geometry can be obtained from solid-state NMR data and a molecular modelling approach.