SOLID-STATE P-31 NMR-STUDIES OF MERCURY(II) PHOSPHONATES - ANISOTROPIES OF THE P-31 CHEMICAL-SHIFT AND THE P-31-HG-199 INDIRECT SPIN SPIN COUPLING

The P-31 powder NMR line shapes of a number of solid mercury(II) phosphonates are analyzed in order to determine the anisotropies in both the P-31 chemical shift and the P-31-Hg-199 indirect spin-spin coupling. The magnitudes and orientation of the principal components of the P-31 chemical shift tensor are determined for diethyl N-phenylphosphoramidate, (EtO)2P(O)NHPh, by using dipolar-chemical shift NMR spectroscopy. Spectral simulations indicate that the most shielded component of the P-31 chemical shift tensor lies along the P = O bond, while the intermediate component, delta-22, lies perpendicular to the N-P = O plane. This information is used to interpret the P-31 NMR line shapes for a series of mercury phosphonate complexes. These spectra indicate the presence of substantial anisotropies in the P-31-Hg-199 indirect spin-spin (J) coupling, ranging from 1500 to 2700 Hz. The large anisotropies in J indicate that mechanisms other than the Fermi contact contribute to the electron-mediated communication between P-31 and Hg-199.