Full NMR spectral assignments of the phospholene chalcogenides 1-12 are presented and their stereochemistry proven. The enantiomeric ratio of any of these compounds can be monitored easily by adding one mole equivalent of the chiral auxiliary Rh(2)[(R)-MTPA](4) (MTPA-H identical with Mosher's acid) and subsequent NMR inspection. Some surprisingly large diastereomeric signal dispersion is observed in the (1)H NMR spectra of the adducts, leading to the conclusion that intramolecular anisotropy interaction between groups inside the ligand molecules exists. The dependence of dispersion effects on the nature of the chalcogenide atom is investigated.

The adducts of dirhodium tetraacylates and phosphines are characterized in solution by 1 H and 31 P NMR spectroscopy at room temperature. A differentiation of the enantiomers of chiral phosphine ligands is easily performed by NMR signal integration after adduct formation with the enantiopure Rh 2 [(R)-(+)-MTPA] 4 complex (Rh*). Stereochemical aspects are discussed in terms of chiral discrimination and adduct diastereomerism. A second type of chiral recognition was discovered, namely, that between two ligand molecules in 2:1 adducts across the Rh 2 [(R)-(+)-MTPA] 4 building block. Conditions for optimizing the experiment for the determination of enantiomeric composition of chiral phosphines by the "dirhodium method" are presented. The possibility of determining absolute configurations of chiral phosphines is briefly discussed.