Thermochemistry of tetrachalcogen-bis-hexafluoroarsenate salts M4(AsF6)2(M=Se or Te) containing lattice-stabilized cyclic M42+cations

✍ Scribed by Iwona Tomaszkiewicz; Jack Passmore; Gabriele Schatte; P.A.G. O'Hare

• Book ID: 102575404
• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 209 KB
• Volume: 28
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1996.0087

✦ Synopsis

The massic energies of combustion of the tetrachalcogen-bis-hexafluoroarsenates of selenium and tellurium in fluorine: Se4(AsF6)2(cr) + 11F2(g) = 4SeF6(g) + 2AsF5(g) Te4(AsF6)2(cr) + 11F2(g) = 4TeF6(g) + 2AsF5(g) have been determined by combustion calorimetry, and from them the standard molar enthalpies of formation have been derived at T = 298.15 K: DfH°m{Se4(AsF6)2} = -(3092.5 2 5.0) kJ•mol -1 ; DfH°m{Te4(AsF6)2} = -(3353.6 2 10.6) kJ•mol -1 , where the uncertainties correspond to twice the standard deviation of the mean. The enthalpy of the reaction: M4(AsF6)2(cr) = 2M2AsF6(cr) is estimated to be positive for M = Te, which indicates that Te 2+ 4 is lattice stabilized in the solid state. For the reaction with M = Se, the uncertainty is very much larger than the enthalpy of reaction, so the thermochemical information allows no firm conclusion to be drawn about the stability of Se 2+ 4 .