Octachalcogen cations Te-8(2+), Se-8(2+), and mixed (Te8-xSex)(8)(2+) stabilized by chlorometallates of Bi, Zr, and Hf: Synthesis and crystal structures of Se-8[Bi4Cl14] and E-8[MCl6] (E = Se, Te; M = Zr, Hf)

The title compounds were obtained by the reaction of elemental chalcogens E (E = Se, Te) with the respective tetrachlorides ECl4 and the Lewis acidic metal halides ZrCl4, HfCl4, and BiCl3. An alternative way, particularly for the preparation of mixed Se/Te-species, is the enlargement of smaller cati onic rings in E-4[MCl6] (M = Zr, Hf) by adding the respective complementary chalcogen. All reactions were carried out in sealed, evacuated glass ampou les at temperatures between 120 degrees C and 220 degrees C, and yielded bl ack crystals of Se-8[Bi4Cl14], (Te5.0Se3.0)[HfCl6], (Te5.3Se2.7)[ZrCl6], (T e6.5Se1.5)[ZrCl6] and Te-8[HfCl6], which have been identified by crystal st ructure analyses. All five compounds contain eight-membered chalcogen rings in an endo-exo-conformation which are isostructural to the known octachalc ogen dications E-8(2+) (E = S, Se, Te). While in (Te5.0Se3.0)[HfCl6], (Te5. 3Se2.7)[ZrCl6], (Te6.5Se1.5)[ZrCl6] and Te-8[HfCl6] the molecular polycatio ns are surrounded by discrete, octahedral [MCl6](2-)counterions, Se-4[Bi4Cl 14] contains a two-dimensional polymeric anion ([Bi4Cl14](2-))(n) built Of a variety of vertex and edge-sharing BiClx-polyhedra (x = 6, 7). The Bi-CI bond lengths are spread over a wide range between 250 and 350 pm.