Cross-Correlation of Nuclear Quadrupolar Interactions as a Probe in Structure Elucidation: Liquid-Phase Nuclear Magnetic Resonance Studies on Bis(hexamethyldisilylamido)mercury(II)

Abstract

The values of longitudinal nuclear spin relaxation rates for the 199Hg (spin-1/2) and 14N (spin-1) nuclei and of the quadrupolar cross-correlation coefficient for the 14N nuclei are determined for a toluene solution of bis(hexamethyldisilylamido)mercury(II) in a broad temperature range. Estimates of the latter quantity were obtained from iterative line shape fits of the 199Hg resonance signals. Sensitivity of the 199Hg resonances to the quadrupolar cross-correlations is because in the temperature range investigated the quadrupolar relaxation rates of the 14N nuclei become comparable to the 199Hg-14N scalar coupling. The data obtained are shown to be consistent with the structure in which the Si2N-Hg-NSi2 skeleton maintains D2d geometry on the time scale of the overall molecular reorientation. Under a well-justified assumption involving the extent of the possible anisotropy of the latter, the principal axes of the 14N electric field gradient tensors, corresponding to the gradients of maximum absolute value...