A nuclear magnetic resonance study of dialkyldithiophosphate complexes : polycrystalline and surface adsorbed

Sammanfattning: 31P, 13C and 207Pb NMR were used to characterize different metal (Ni, Zn, Pb) dialkyldithiophosphate complexes. Eight different sodium or potassium dialkyldithiophosphate salts (alkyl groups R=ethyl-, n-propyl, iso-propyl, n- butyl, iso-butyl, sec-butyl, iso-amyl and cyclo-hexyl) were used as starting materials. The metal complexes studied are mononuclear, binuclear, tetranuclear or polynuclear and the structural diversity is reflected in different 31P chemical shifts and chemical shift aniostropies of the complexes. A correlation between the 31P chemical shift tensor principal value d22 and the S-P-S angle of the complexes was revealed. The ligands were also adsorbed on the surface of synthetic ZnS and PbS and studied by 31P CP/MAS NMR: spectra of the dry samples showed that in both cases chemisorption of the ligands on the mineral surfaces occured. The ligands chemisorbed on ZnS have a bridging coordination, while the coordination of the ligand to PbS is terminal. Products of oxidation and hydrolysis were also found on the mineral surfaces; disulfides were detected on the surface of ZnS and monothiophosphates and orthophosphates on the surface of PbS. After three months of storing of the PbS samples, more hydrolysis products were formed as well as precipitated lead(II) dithiophosphate complexes.