1,1-Di­methyl­biguanidium tetra­bromo­thallate(III)

The title compound, (C₄H₁₂N₅)[TlBr₄], was crystallized from an aqueous solution containing [Tl(DMSO)₆](ClO₄)₃, N,N-di­methyl­biguanide hydro­chloride and NaBr in a 1:1:3 molar ratio (DMSO is di­methyl sulfoxide). The geometry of [TlBr₄]⁻ is a slightly distorted tetrahedron. The cation is protonated at one of the imino groups, and through this an intramolecular N—H⋯N hydrogen bond is formed, which stabilizes the conformation of the cation in the structure.