Far-infrared and Raman spectra of crystalline tetra-alkylammonium trihalogenomercurate(II) salts. Evidence for monomeric or halogen-bridged associated anions depending on the cation
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 16,p. 1593-1596
- https://doi.org/10.1039/dt9760001593
Abstract
A study has been made of the far-infrared (20–400 cm–1) and Raman spectra of eight compounds of type [NR4][HgX3](R = Me, Et, Prn, or Bun; X = Cl, Br, or I) and of [SMe3][HgI3] in the solid state. Solution-phase Raman data have also been obtained. For R = Et and X = Cl two crystalline modifications have been identified. The low-temperature α form has vibrational spectra explicable in terms of an essentially monomeric anionic structure, whereas the β form, stable above 71 °C, clearly contains strong halide-bridged groups. The structures of the other compounds have been deduced by comparison with the data on α- and β-[NEt4][HgCl3]. Thus associated anionic structures are present also in [NEt4][HgX3](X = Br or I), [NPrn 4][HgCl3], and [NBun 4][HgI3]. Evidently the weak halogen bridging found in the crystal structures of [SMe3][HgI3] and [NMe4][HgCl3] may be disregarded in qualitative interpretation of the vibrational data; the spectra of [NMe4][HgX3](X = Br or I) may similarly be described in terms of monomeric anionic structures.Keywords
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