Arene−Mercury Complexes Stabilized Aluminum and Gallium Chloride:  Synthesis and Structural Characterization

• Published in: Journal of the American Chemical Society 2001-11, Vol.123 (45), p.11219-11228
• Main Authors: Borovik, Alexander S, Bott, Simon G, Barron, Andrew R
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja011003u

Reaction of HgCl2 with 2 equiv of MCl3 in an aromatic solvent yields Hg(arene)2(MCl4)2 where, arene = C6H5Me, M = Al (1), Ga (2); arene = C6H5Et, M = Al (3) and Ga (4); o-C6H4Me2, M = Al (5), Ga (6); C6H3-1,2,3-Me3, M = Al (7) and Ga (8). The solid-state structures of compounds 1−5 and 7 have been determined by X-ray crystallography. In the solid state, compounds 1−4 and 7 exist as neutral complexes in which two arenes are bound to the mercury, and the MCl3 groups are bound through bridging chlorides to the mercury; compound 5 exists as a cation−anion pair [Hg(o-C6H4Me2)2(AlCl4)][AlCl4]. However, in solution compounds 1−8 all exist as neutral complexes. The structures of Hg(arene)2(AlCl4)2 and [Hg(arene)2(AlCl4)]+ have been determined by DFT calculations {B3LYP level} to facilitate the assignment of the 13C CPMAS NMR spectra and are in good agreement with the X-ray diffraction structures of compounds 1 and 5. Reaction of HgCl2 with MCl3 in benzene, m-xylene, and p-xylene results in the formation of liquid clathrates whose spectroscopic characterization is consistent with ionic structures, [Hg(arene)2(MCl4)][MCl4]. The calculated energy difference between Hg(C6H5Me)2(AlCl4)2 and [Hg(C6H5Me)2(AlCl4)][AlCl4] is discussed with respect to the structure of compound 5 in the solid state versus solution state and the proposed speciation in the liquid clathrates.