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From thallium(III) bromide solution, the unsubstituted pyridinium cation yields a complex (1) with the [Tl 2 Br 9 ] 3À anionic stoichiometry. The Raman spectrum and single-crystal X-ray crystallographic analysis showed that the salt contains independent [TlBr 4 ] À and bromide anions. A variety of mono-and disubstituted pyridinium cations were also employed in similar syntheses. The 2-bromopyridinium cation gave a salt 2 with [TlBr 5 ] 2À stoichiometry, but the crystal structure revealed very weakly interacting [TlBr 4 ] À and bromide anions with a Tl ¥¥¥ Br À distance of 4.1545(6) ä. The 2-(ammoniomethyl)pyridinium and 2-amino-4-methylpyridinium cations yielded complexes containing [TlBr 5 ] 2À (3) and [TlBr 4 ] À (4) species, respectively, which were confirmed by Raman spectroscopy and X-ray crystallographic analyses. For 3, the [TlBr 5 ] 2À anion has a highly distorted trigonal bipyramidal conformation with one long axial Tl ¥¥¥ Br bond of 3.400(2) ä. Microanalytical results in conjunction with Raman spectra from a further five salts confirmed that they all contain the simple [TlBr 4 ] À anion. NÀH ¥¥¥ Br Hydrogen bonds clearly influence the nature of the anionic species obtained in these systems.

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