Mixed Pentele-Chalcogen Cationic Chains from Aluminum
and Gallium Halide Melts
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Abstract
The
reactions of tellurium or selenium with bismuth or antimony
in chloridogallate and iodidoaluminate melts in the presence of group
15 trihalides as weak oxidants yielded the compounds (Sb<sub>2</sub>Te<sub>2</sub>)[GaCl<sub>4</sub>] (<b>1</b>), (Sb<sub>2</sub>Te<sub>2</sub>)I[AlI<sub>4</sub>] (<b>2</b>),
(Bi<sub>2</sub>Te<sub>2</sub>)Cl[GaCl<sub>4</sub>] (<b>3a</b>), (Bi<sub>2</sub>Se<sub>2</sub>)Cl[GaCl<sub>4</sub>] (<b>3b</b>), (Sb<sub>3</sub>Te<sub>4</sub>)[GaCl<sub>4</sub>] (<b>4</b>), and (SbTe<sub>4</sub>)[Ga<sub>2</sub>Cl<sub>7</sub>] (<b>5</b>). In the crystal structures one-dimensional
polymeric cations (Sb<sub>2</sub>Te<sub>2</sub><sup>+</sup>)<sub><i>n</i></sub> (<b>1</b>), (Sb<sub>2</sub>Te<sub>2</sub><sup>2+</sup>)<i><sub>n</sub></i> (<b>2</b>), (Bi<sub>2</sub>Te<sub>2</sub><sup>2+</sup>)<i><sub>n</sub></i> (<b>3a</b>), (Bi<sub>2</sub>Se<sub>2</sub><sup>2+</sup>)<sub><i>n</i></sub> (<b>3b</b>), (Sb<sub>3</sub>Te<sub>4</sub><sup>+</sup>)<sub><i>n</i></sub> (<b>4</b>), and
(SbTe<sub>4</sub><sup>+</sup>)<sub><i>n</i></sub> (<b>5</b>) are present. The polymeric cationic strands in <b>2</b>, <b>3a</b>, <b>3b</b>, and <b>4</b> consist of
pentele/chalcogen dumbbells, which are connected to ladder-shaped
bands. The strands in <b>1</b> and <b>5</b> consist of
condensed rings that involve four-membered Sb<sub>2</sub>Te<sub>2</sub> rings for <b>1</b>, and five-membered SbTe<sub>4</sub> rings
for <b>5</b>. The counteranions are the weakly coordinating
[GaCl<sub>4</sub>]<sup>−</sup>, [AlI<sub>4</sub>]<sup>−</sup>, and [Ga<sub>2</sub>Cl<sub>7</sub>]<sup>−</sup> in addition
to Cl<sup>–</sup> and I<sup>–</sup> anions, which are
coordinated to the atoms of the cations. The crystal structures of <b>1</b>–<b>4</b> are characterized by a statistical
disorder in the anions with alternatively occupied positions for the
Al and Ga atoms. For <b>4</b> superstructure reflections appear
in the diffractions patterns, indicating a partial order. A correct
assignment of the Sb and Te positions in the cation of <b>5</b> was achieved by periodic quantum-chemical calculations, which were
performed via a Hartree–Fock density functional theory hybrid
method. A clear preference of the 4-fold coordinated site was obtained
for Sb