A Solid-State 199Hg NMR Study of Mercury Halides
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The principal elements of the 199Hg chemical-shift (CS) tensors of the mercuric halides (HgX2, X = F, Cl, Br, and I) and the mercurous halides (Hg2X2, X = F and Cl) were determined from spectra of static polycrystalline powders and from magic-angle spinning (MAS) spectra. The CS tensors of both HgCl2 and Hg2Cl2 are axially symmetric (η = 0) within experimental error, differing from literature reports of η=0.12 and η=0.14, respectively. The principal elements of the axially symmetric CS tensor in HgBr2 were also measured using a static sample, and the wideline spectra of HgF2 and HgI2 (red polymorph) give chemical-shift tensors that suggest, within experimental error, that the mercury sits in sites of cubic symmetry. The 199Hg CS tensor for Hg2F2 is asymmetric. Experiments with static polycrystalline samples may allow the determination of the elements of the 199Hg CS tensors even when MAS fails to completely average the dipolar coupling of the spin-½ 199Hg and the quadrupolar halide nucleus.