Two ammonium tetra­chlorido­aluminate salts: how a twinned ortho­rhom­bic structure emulates a trigonal crystal system

Tetra­butyl­ammonium tetra­chlorido­aluminate benzene hemisolvate crystallizes with discrete cations, anions and solvent mol­ecules, and the benzene mol­ecule is located on a centre of inversion. Tetra­ethyl­ammonium tetra­chlorido­aluminate also crystallizes with discrete cations and anions, and forms crystals which appear trigonal but are actually ortho­rhom­bic. With the additional reflections of the second and third domains of this nonmerohedral twin, a trigonal lattice is emulated, although the correct crystal system is ortho­rhom­bic.