[Te 8 ] 2 [Ta 4 O 4 Cl 16 ]: A Two‐dimensional Tellurium Polycation obtained via Ionic Liquid‐Based Synthesis

By reaction of elemental tellurium, tellurium(IV) chloride, tantalum(V) chloride and tantalum(V) oxychloride in the ionic liquid [BMIM]Cl ([BMIM]Cl:1‐Butyl‐3‐methylimidazolium chloride),[Te 8 ] 2 [Ta 4 O 4 Cl 16 ] is obtained in the form of lucent black crystals. The title compound consists of infinite [Te–Te–(Te 6 )] n 2+ chains (Te–Te: 264.9(1)–284.3(1) pm) and isolated [Ta 4 O 4 Cl 16 ] 4– anions. The [Te–Te–(Te 6 )] n 2+ chains are interconnected to form a two‐dimensional tellurium network (Te–Te: 335.9 pm). Due to this interaction the [Te–Te–(Te 6 )] n 2+ chains in [Te 8 ] 2 [Ta 4 O 4 Cl 16 ] show an arrangement that differs significantly from known polycationic [Te 8 ] n 2+ chains. The two‐dimensional tellurium network is finally separated by tetrameric, corner‐sharing oxidochloridotantalate anions [(TaO 2/2 Cl 4/1 ) 4 ] 4– that are firstly observed. The composition of [Te 8 ] 2 [Ta 4 O 4 Cl 16 ] is confirmed by EDX analysis; its optical band gap is estimated to 1.1–1.2 eV via UV/Vis spectroscopy.