The Barium Oxotellurate(IV) Bromides Ba₆Te₁₀O₂₅Br₂ and Ba₃Te₃O₈Br₂ with Channel Structures

Abstract

Abstract Two new barium oxotellurate(IV) bromides with sum formula Ba 6 Te 10 O 25 Br 2 and Ba 3 Te 3 O 8 Br 2 were obtained under hydrothermal conditions and were characterized by single‐crystal X‐ray diffraction. In the crystal structures of both compounds a three‐dimensional Ba/Te/O network is perforated by channels, into which the lone pairs E of the Te IV atoms protrude and in which the Br – anions are located. Ba 6 Te 10 O 25 Br 2 { Aea 2, Z = 8, a = 11.4707(9) Å, b = 31.140(2) Å, c = 18.3216(14) Å, 9331 F 2 data, 392 variable parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0376} can be described as a fourfold super structure derived from an idealized basic structure in space group Pmmn . The main building blocks of the super structure are nine crystallographically independent [TeO 3+1 ] units and one trigonal‐pyramidal [TeO 3 ] unit, which share corners and edges to form wavy layers parallel to (001) that are connected by seven independent Ba 2+ ions. The three independent Br – anions are situated in channels parallel to [100], leading to overall coordination numbers of the cations ranging from eight to eleven. In the crystal structure of Ba 3 Te 3 O 8 Br 2 { Pnma , Z = 4, a = 12.6226(8) Å, b = 5.9663(4) Å, c = 18.1112(12) Å, 5897 F 2 data, 88 variable parameters, R [ F 2 > 2 σ ( F 2 )] = 0.0260} the oxotellurate(IV) anions consist of an isolated [TeO 3 ] unit and a condensed [Te 2 O 5 ] 2– group. They coordinate to the three independent Ba 2+ ions to form channels extending parallel to [010]. The overall coordination number of all cations is eight whereby each of them is bonded at least to one of the two independent Br – anions in the channels in the form of distorted coordination polyhedra.