ISSN:
1434-1948
Keywords:
Mercury cations
;
Subvalent compounds
;
Ab initio calculations
;
Liquid X-ray scattering
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Hg2Cl2 dissolves in GaCl3/benzene solution to yield Hg22+ and chlorogallate(III) ions, GanCl3n+1-. In such solutions, Hg22+ can be reduced to Hg32+ by metallic mercury. Solubility measurements show that one mol of Hg is oxidised per mol of Hg22+. The Hg32+ ion gives a strong band at 110 cm-1 in the Raman spectrum and Hg-Hg correlations at about 2.60 and 5.15 Å in the radial distribution function obtained by liquid X-ray scattering. - Hg32+ can also be synthesised in high yield by direct oxidation of metallic mercury by GaIII in GaCl3/benzene solution. In contrast, mercury is insoluble in neat liquid GaCl3 and only sparingly soluble in GaCl3/KCl melts. It therefore seems likely that the thermodynamic stabilisation of subvalent mercury species in benzene solution not only relies on the traditional acid stabilisation provided by the hard Lewis acid GaCl3, but also on a “soft-base stabilisation” provided by interactions between the aromatic molecules and the cations. Evidence for such specific interactions between Hgm2+ cations and C6H6 are observed in the Raman spectra: The totally symmetric C6H6 band at 991 cm-1 is found to split in the presence of Hgm2+ ions and to give new peaks at 978 (m = 2) and 982 (m = 3) cm-1. - In order to further elucidate the cluster-arene interactions, ab initio and density functional calculations were performed for the model compounds Hgm(C6H6)22+ and HgmCl2(C6H6)2, m = 2 and 3. The calculations show that both models represent coordinations modes which are feasible for Hgm2+ ions. However, the calculated vibrational frequencies for the Hgm(C6H6)22+ models with η1/quasi-η3 coordination of the benzene molecules along the Hg-Hg vector are most consistent with the body of experimental and literature data. The counterions are thus suggested to occupy secondary coordination sites.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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