An NMR Study of Phenyl- and Diphenylphosphine Alkali Metal Salts

Abstract

The 1H, 13C, and 31P NMR spectra were observed for the title salts in several solvents. The formation of the salts by the deprotonation of the neutral precursors causes significant changes in their NMR parameters. First, the delocalization of the excess charges into the phenyl ring of the salts was confirmed from the 1H and 13C chemical-shift data. Second, the parameters concerned with the center of the anions are dependent on the circumstances of the center atom, phosphorus, such as the hybridization. The results are discussed in terms of the effects of the counter cations and the solvents. Third, a strong polar solvent, HMPA, exerts significant effects on the chemical shifts and the one-bond 13C–31P coupling constants. These parameter changes are explained in terms of an equilibrium between two kinds of ion-pairs (contact ion-pairs and solvent-separated ion-pairs). The parameters obtained in this solvent, HMPA, correspond to those of the solvent-separated ion-pairs or the free anions.