Determination of spin parameters reflected in the nuclear magnetic resonance powder patterns for two equivalent 31P nuclei in Lawesson's reagent.

The nuclear magnetic resonance (NMR) powder patterns observed for the 31P spin pair in Lawesson's reagent (1) were analyzed. Using an efficient procedure, wide ranges of the spin parameters were examined to determine whether they might reproduce the experimental one-dimensional (1D) spectrum of the present A2 spin system. It was demonstrated that the parameters were not uniquely determined from the 1D powder pattern only, but a significant reduction of their uncertainties was realized using the two-dimensional (2D) powder pattern. The molecular structure of 1 was discussed in terms of the refined spin parameters.