Untersuchungen zur Polymorphie der Cäsium-Dodekahalogeno-closo-Dodekaborate Cs2[B12X12] (X = Cl–I)

Thermoanalytic DSC and temperature-dependent X-ray diffraction investigations on the cesium dodecahalogeno-closo-dodecaborates Cs2[B12X12] (X = Cl–I) have revealed solid-solid phase transitions from their trigonal room-temperature α-forms (e.g. α-Cs2[B12Cl12]: a = 959.67(3) pm, c = 4564.2(2) pm, Z = 6, space group R$\overline{3}$) into cubic high-temperature modifications. The isotypic title compounds crystallize in the space group Pm$\overline{3}$n (e.g. β-Cs2[B12Cl12]: a = 1051.98(6) pm, Z = 2) with a W3O-type defect structure. The statistic occupation of six possible positions with only four Cs+ cations results in a cation-deficient A2B arrangement for Cs2[B12X12]. Upon cooling the β-phase, a third polymorph was observed, which also crystallizes in the cubic system, but now in the space group Ia$\overline{3}$d (e.g. γ-Cs2[B12Cl12]: a = 2102.2(3) pm, Z = 16), and has to be regarded as a phase with only a partially disordered cation substructure. In this crystal structure the [B12X12]2− anions exhibit a NaTl-type arrangement, in which the Cs+ cations occupy suitable interstices. The phase transitions of the differently halogenated cesium salts follow no specific trend as the transition from the trigonal α- to the cubic β-form occurs at 178 °C for the chlorinated, at 270 °C for the iodinated and at 325 °C for the brominated examples. On further heating however, β-Cs2[B12I12] starts to decompose at 945 °C first, followed by β-Cs2[B12Br12] and β-Cs2[B12Cl12] at 959 °C and 983 °C, respectively.

Hydrolysis of Cellulose in the Presence of Catalysts Based on Cesium Salts of Heteropolyacids

The catalytic properties of cesium salts of heteropolyacids with the composition Cs4-хHхSiW12O40 (х = 3 and 3.5), Cs3-хHхPMo12O40 and Cs3-хHхPW12O40 (х = 2 and 2.5) were studied in the hydrolysis of cellulose to glucose at 180 °C in an argon atmosphere. Glucose was shown to be the main product of the reaction. The maximum yield reached 23% in the presence of Cs3HSiW12O40 for 1 h of the reaction. Specific surface area was supposed to affect the catalyst efficiency. It was found that in the presence of the indicated salts the reaction is heterogeneous and homogeneous, which is caused by leaching of the active component to the solution. The obtained materials were shown to be more efficient in comparison with the systems reported in the literature.

Novel 3D cesium(i)-based EMOFs of nitrogen-rich triazole derivatives as “green” orange-light pyrotechnics

An ingenious strategy based on energetic metal–organic frameworks with cesium salts for green and practical pyrotechnic composition has been described.

One-pot synthesis of formic acid via hydrolysis–oxidation of potato starch in the presence of cesium salts of heteropoly acid catalysts

Influence of composition of catalysts based on heteropoly acid cesium salts on formic acid production via starch hydrolysis–oxidation was investigated.