P-31 NMR-STUDIES OF SOLID TETRAETHYLDIPHOSPHINE DISULFIDE - A REINVESTIGATION OF THE P-31,P-31 SPIN-SPIN COUPLING TENSER

A P-31 NMR study of powder samples of tetraethyldiphosphine disulfide (TEPS) has been undertaken in order to compare the results of variable-field and 2D spin-echo experiments with those of an earlier single-crystal P-31 NMR study of TEPS (Tutunjian and Waugh, 1982). A significant discrepancy in the value of the effective dipolar coupling constant, R(eff,) which is the difference between the direct dipole-dipole coupling constant and one-third of the anisotropy in the indirect spin-spin coupling interaction, prompted a reinvestigation of the single-crystal P-31 NMR study of TEPS. We also redetermined the crystal structure of TEPS by X-ray diffraction to obtain more accurate geometrical parameters. The results of our single-crystal P-31 NMR experiment confirm the data determined from our P-31 NMR studies of powder samples. We obtained a value of R(eff) of 1650 +/- 10 Hz, compared to the previously reported value of 1100 Hz; the direct dipolar coupling constant calculated from the P,P bond length is 1805 Hz. The principal components of the phosphorus chemical shift tenser are delta(11) = 108 ppm, delta(22) = 98 ppm, and delta(33) = -54 ppm. The most shielded direction is located within the SPPS plane and makes an angle of 2 degrees with the direction of the PS bond.