Different potassium salts and zinc(II) and nickel(II) O,O'-dialkyldithiophosphate complexes were studied by solid-state 31P CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the 31P chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew , while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the δ22 component of the 31P chemical shift tensor and the S-P-S bond angle in the O,O'-dialkyldithiophoshate zinc(II) and nickel(II) complexes was found: δ22 increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100 to 120, while the other two principal values of the tensor, δ11 and δ33, are almost conserved. This eventually leads to the change in sign for in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-dialkyldithiophoshate group forming chelating four-membered P<>Me heterocycles
Validerad; 2005; 20061219 (bajo)