- The First Step of the Oxidation of Elemental Sulfur: Crystal Structure of the Homopolyatomic Sulfur Radical Cation [S8].+
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The oxidation of elemental sulfur in superacidic solutions and melts is one of the oldest topics in inorganic main group chemistry. Thus far, only three homopolyatomic sulfur cations ([S4]2+, [S8]2+, and [S19]2+) have been characterized crystallographically although ESR investigations have given evidence for the presence of at least two additional homopolyatomic sulfur radical cations in solution. Herein, the crystal structure of the hitherto unknown homopolyatomic sulfur radical cation [S8].+ is presented. The radical cation [S8].+ represents the first step of the oxidation of the S8 molecule present in elemental sulfur. It has a structure similar to the known structure of [S8]2+, but the transannular sulfur???sulfur contact is significantly elongated. Quantum-chemical calculations help in understanding its structure and support its presence in solution as a stable compound. The existence of [S8].+ is also in accord with previous ESR investigations.
- Derendorf, Janis,Jenne, Carsten,Ke?ler, Mathias
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supporting information
p. 8281 - 8284
(2017/06/30)
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- [Li(XeF2)n](AF6) (A = P, As, Ru, Ir), the first xenon(II) compounds of lithium. Synthesis, Raman spectrum, and crystal structure of [Li(XeF2)3](AsF6)
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The reactions between compounds of the type MAF6 (M = alkali metal; A = P, As, V, Ru, Ir, Sb, Nb, Ta) and xenon difluoride were studied in anhydrous hydrogen fluoride solvent. The coordination products [M(XeF 2)n]AsF6 were only observed in the case of LiAF6 (A = P, As, Ru, Ir), and the crystal structure of [Li(XeF 2)3]AsF6 was determined (monoclinic space group P21 with a = 6.901(9) A, b = 13.19(2) A, c = 6.91(1) A, β = 91.84(2), and Z = 2). The coordination sphere of lithium is comprised of six F atoms. The compound series was also characterized by Raman spectroscopy.
- Tavcar, Gasper,Zemva, Boris
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p. 4319 - 4323
(2013/05/22)
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- Thermodynamic properties and decomposition of lithium hexafluoroarsenate, LiAsF6
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The heat capacity of lithium hexafluoroarsenate is determined in the temperature range 50-750 K by adiabatic and differential scanning calorimetry techniques. The thermodynamic properties of LiAsF6 under standard conditions are evaluated: Cp0 (298.15 K)= 162.5 ± 0.3 J/(K mol), S0(298.15 K) = 173.4 ± 0.4 J/(K mol), Φ0(298.15 K) = 81.69 ± 0.20 J/(K mol), and H 0(298.15 K) - H0(0) = 27 340 ± 60 J/mol. The C p(T) curve is found to contain a lambda-type anomaly with a peak at 535.0 ± 0.5 K, which is due to the structural transformation from the low-temperature, rhombohedral phase to the high-temperature, cubic phase. The enthalpy and entropy of this transformation are 5.29 ± 0.27 kJ/mol and 10.30 ± 0.53 J/(K mol), respectively. The thermal decomposition of LiAsF6 is studied. It is found that LiAsF6 decomposes in the range 715-820 K. The heat of decomposition, determined in the range 765-820 K using a sealed crucible and equal to the internal energy change ΔU r(T), is 31.64 ± 0.08 kJ/mol.
- Gavrichev,Sharpataya,Gorbunov,Golushina,Plakhotnik,Goncharova,Gurevich
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p. 175 - 182
(2008/10/08)
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