Preparation and structural organisation of heteroleptic tetraphenylantimony(V) complexes comprising unidentately and bidentately coordinated O,O′-dialkyldithiophosphate groups: Multinuclear (13C, 31P) CP/MAS NMR and single-crystal X-ray diffraction studies

Article abstract of DOI:10.1016/j.ica.2007.02.044

O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C₆H₅)₄{S₂P(OR)₂}] (R = C₃H₇, i-C₄H₉) were prepared and studied by means of ¹³C, ³¹P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate ligands in their molecular structures (i.e., S,S′-bidentate chelating and S-unidentately coordinated, respectively). To characterise quantitatively phosphorus sites in both species of dithiophosphate ligands, ³¹P chemical shift anisotropy parameters (δ_aniso and η) were calculated from spinning sideband manifolds in MAS NMR spectra. The ³¹P chemical shift tensors for the bidentate chelating and unidentately coordinated dithiophosphate ligands display a profoundly rhombic and nearly axially symmetric characters, respectively.