AB-INITIO IGLO CALCULATIONS OF P-31 NMR SHIELDING TENSORS OF THIOPHOSPHORYL COMPOUNDS .1. DITHIADIPHOSPHETANES AND DITHIOXOPHOSPHORANES

By means of the IGLO method the P-31 NMR chemical shift, delta(iso) th e principal values, sigma(ii), and the orientation of the principal ax es of the shielding tenser were calculated for a number of dithiadipho sphetanes [RP(S)S](2) and of dithioxophosphoranes RPS(2) with R = H, C H3 or C6H5. The calculated compare well to the available experimental data from solid-state NMR and can be taken as predictions where no exp erimental data are available. The dependence of the principal values s igma(ii) on geometry changes and the substitution was studied. The shi elding tensors were calculated as sums of contributions of localized m olecular orbitals. These contributions were used to discuss the effect s observed. They provide valuable insights into relationships between geometrical structure and the principal values of sigma.