title: Two ammonium tetrachloridoaluminate salts: how a twinned orthorhombic structure emulates a trigonal crystal system.
abstract: We have determined the crystal structures of two tetrachloridoaluminate salts. Tetrabutylammonium tetrachloridoaluminate benzene hemisolvate, (C16H36N)[AlCl4]·0.5C6H6, (I), crystallizes with discrete cations, anions and solvent molecules. The benzene molecule is located on a centre of inversion. The structure of the benzene-free polymorph has been determined previously. Tetraethylammonium tetrachloridoaluminate, (C8H20N)[AlCl4], (II), 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.
authors.affiliation: Institut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Tillmann
authors.affiliation: Institut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany.
authors.forename: Hans-Wolfram
authors.initials: HW
authors.lastname: Lerner
authors.affiliation: Institut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
keywords: Al...Al contacts; N...Al contacts; benzene solvate; crystal structure; tetrabutylammonium; tetrachloridoaluminate salts; tetraethylammonium; twinning