Structural Diversity in Thallium Chemistry. Part VI

Abstract

New bromothallate(III) complexes have been synthesized using eleven organoammonium cations related to others employed previously. The crystal structure determinations of eight of these have been performed. The diethylenetriammonium cation yields the first compound containing [TlBr 6 ] 3À as the only anionic species, while the N,N,N',N'',N''-pentamethyldiethylenetriammonium cation gave a mixed salt containing discrete [TlBr 4 ] À and Br À ions, in which the [TlBr 4 ] À unit does not participate in hydrogen bonding. In the pyrazolinium mixed salt, both the [TlBr 4 ] À and Br À ions are hydrogen-bonded to cations and disposed in an arrangement similar to a [Tl 2 Br 9 ] 3À unit. The triethylenediammonium dication gives a compound in which a highly distorted trigonal bipyramidal [TlBr 5 ] 2À system is present, while the 1benzylpiperazinium compound also shows a very weak [TlBr 4 ] À and Br À interaction. Six other monovalent cations provided [TlBr 4 ] À derivatives that were characterized either crystallographically or via their Raman spectra. In a comprehensive structural summary, the various interactions between cations and bromothallate(III) anionic groupings, giving rise to the structural diversity described in this and previous reports, are discussed in terms of the cation charge, quaternization and steric influence, NÀH ··· Br hydrogen bonding, and secondary bonds present in the compounds.