Structural Diversity in Thallium Chemistry. Part V

From thallium(III) bromide solution, the unsubstituted pyridinium cation yields a complex ( 1 ) with the Tl₂Br₉]^3? anionic stoichiometry. The Raman spectrum and single‐crystal X‐ray crystallographic analysis showed that the salt contains independent TlBr₄]^? 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 TlBr₅]^2? stoichiometry, but the crystal structure revealed very weakly interacting TlBr₄]^? and bromide anions with a Tl ???Br^? distance of 4.1545(6) Å. The 2‐(ammoniomethyl)pyridinium and 2‐amino‐4‐methylpyridinium cations yielded complexes containing TlBr₅]^2? ( 3 ) and TlBr₄]^? ( 4 ) species, respectively, which were confirmed by Raman spectroscopy and X‐ray crystallographic analyses. For 3 , the TlBr₅]^2? anion has a highly distorted trigonal bipyramidal conformation with one long axial Tl ???Br bond of 3.400(2) Å. Microanalytical results in conjunction with Raman spectra from a further five salts confirmed that they all contain the simple TlBr₄]^? anion. N? H ???Br Hydrogen bonds clearly influence the nature of the anionic species obtained in these systems.