Deuterium Quadrupole Coupling Constants and Asymmetry Parameters in Bridging Metal Hydride Complexes

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The deuterium quadrupole coupling constants and the asymmetry parameters for six bridging metal hydrides, [Et4N][2HCr2(CO)l0], [(Ph3P)2N][2HCr2(CO)10], [Ph4P][2HCr2(CO)10], [Et4N][2HW2(CO)10], [(Ph3P)2N][2HW2(CO)10], and [Ph4P] [2HW2(CO)10], were determined from the Levenberg-Marquardt nonlinear least-squares fit of the solid-state deuterium NMR powder patterns. The quadrupole coupling constant (absolute value) varies from 54.1 (8) to 90.4 (2) kHz; the asymmetry parameter ranges from 0.027 (3) to 0.31 (2). The relationships between the quadrupole coupling constant and M-H bond length and between the asymmetry parameter and the M-H-M bond geometry are discussed on the basis of a point charge model. In order to assess motional averaging at the deuterium site, the temperature dependence of the 2H NMR spectrum for two bridging metal hydrides was examined at 140, 200, and 300 K. In addition, the isotropic chemical shifts have been obtained from 1H CRAMPS. These NMR results are highly pertinent to NMR spectroscopy of adsorbed hydrogen on metal surfaces. The solid-state structure of [Ph4P][2HCr2(CO)10] has been determined by X-ray diffraction. © 1991, American Chemical Society. All rights reserved.

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Journal of the American Chemical Society

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