The High‐Pressure Polymorph of Ca4Te5O14 and the Mixed‐Valent Compound Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3. Issue 22 (4th July 2016)

• Record Type: Journal Article
• Authors: Weil, Matthias; Heymann, Gunter; Huppertz, Hubert
• Is Part Of: European journal of inorganic chemistry. Issue 22(2016)
• Page Start: 3574
• Page End: 3579
• Publication Date: 2016-07-04
• Subjects: High‐pressure chemistry -- Polyoxometalates -- Tellurium -- Calcium; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201600429
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : A high‐pressure/high‐temperature experiment based on the multi‐anvil technique has yielded a high‐pressure (HP) modification of Ca4 Te5 O14 (I ) from the starting materials Ca(OH)2 and TeO2 . Reaction with the boron nitride crucible used in the high‐pressure set‐up led also to the formation of the mixed‐valent Te IV, VI borate Ca13 Te VI 2/3 Te IV 3.75 O15 (BO3 )4 (OH)3 (II ) as a minor phase. The crystal structures of both compounds were determined by single‐crystal X‐ray diffraction [I : P 21 / c, Z = 4, a = 11.0272(1), b = 12.0588(1), c = 10.1038(1) Å, β = 91.849(1)°, R 1( F 2 ) = 0.0317, wR 2( F 2 ) = 0.0459;II : P 63 / m, Z = 2, a = 9.0890(13), c = 18.731(4) Å, R 1( F 2 ) = 0.0401, wR 2( F 2 ) = 0.0867]. The principal building units of HP‐Ca4 Te5 O14, namely [CaO x ] ( x = 7, 8) and Te IV O3 and Te IV O4 polyhedra, are similar to those of the ambient modification, but the structural set‐up is markedly different in the two structures with an increase in density of about 6.6 %. Ca13 Te VI 2/3 Te IV 3.75 O15 (BO3 )4 (OH)3 is the first compound known so far to contain both oxotellurate and oxoborate units. The most remarkable feature of its disordered crystal structure is the centrosymmetric Te3 O6 unit consisting of a Te VI O6 octahedron sharing opposite faces with two trigonal Te IV O3 pyramids. The face‐sharing of Te VI and Te IV oxopolyhedra is unprecedented in the crystal chemistry of oxotellurates. In both structuresI andII, the lone‐electron pairs of the Te IV atoms are stereochemically active. Abstract : Two new structure types have been elucidated during the high‐pressure synthesis of calcium oxotellurates. The high‐pressure polymorph of Ca4 Te5 O14 is compared with its ambient counterpart and Ca13 Te VI 2/3 Te IV 3.75 O15 (BO3 )4 (OH)3 is the first phase reported to contain both oxoborate and oxotellurate units. Face‐sharing of Te VI and Te IV oxopolyhedra in the crystal structure of the latter is unprecedented in the crystal chemistry of oxotellurates.