A second polymorph of 1,1,4,4-tetramethylpiperazinium pentabromothallate(III)

A new polymorph of the title compound, (C8H20N2)[TlBr5], contains cations located about crystallographic centres of inversion and trigonal-bipyramidal anions which have a C2 axis passing through the equatorial plane of the anion. The anion has the least distorted geometry seen so far in any structure possessing this anion and the axial Tl-Br bonds are about 0.13 A longer than the equatorial Tl-Br bonds, consistent with related structures. The anion in the initially reported polymorph has lower symmetry and a greater distortion of the trigonal-bipyramidal coordination.