Solid States NMR Studies of Metal Hydrides

Both conventional and multiple pulse proton NMR studies of the compounds H2Os3(CO 10, H4Ru4(CO)12, and H4Os4(CO)12 as well as multiple pulse studies of CaH2, SrH2, and BaH2 are reported. Chemical shift tensors for protons directly bonded to heavy metal atoms in the metal carbonyl compounds are found to have an isotropic value close to that observed in solution and are found to have an anisotropy of less than 30 ppm. The temperature dependent spectra of H4Ru4(CO)12 indicates the presence of anisotropic proton reorientation at room temperature. The isotropic proton chemical shift for the ionic solids CaH2, SrH2, and BaH2 are found in the range ō= 0 ppm to ō= -10 ppm, and a trend in the isotropic value to shift toward higher field as a function of cation electronegativity is noted. Structured proton NMR lineshapes, observed by conventional pulse NMR, are reported for the metal cluster carbonyl compounds; and the results are interpreted in terms of four dipolar coupled spin ½ nuclei. Contributions to the lineshapes from heteronuclear dipolar interaction with a Zeeman perturbed quadrupolar nucleus, indirect nuclear coupling, and restricted motion are discussed.