Thermochemistry of octasulfur-bis-hexafluoroarsenate S8(AsF6)2 containing the lattice-stabilized S82+

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

“…Otherwise, the calorimetric techniques were similar to those used previously in our study of S 8 (AsF 6 ) 2 . (3) Because of the reactivity of the compounds toward F 2 (g), our standard (bomb + tank) combustion vessel (19) had to be used. The tank was charged with pure F 2 (g) to a pressure of 1 MPa at T 1 296 K; the corresponding amount of substance n(F 2 ) 1 0.1 mol.…”

“…The synthesis of Se 4 (AsF 6 ) 2 was carried out in a one-bulb 50-cm 3 Pyrex glass vessel equipped with a condenser, by a modification of the procedure described elsewhere, (17) and Te 4 (AsF 6 ) 2 was prepared in a two-bulb 25-cm 3 Pyrex glass vessel equipped with two Teflon-stemmed glass valves (J. Young) † and a medium sintered glass frit, also by a modification of the procedure described previously.…”

“…(3) Although the latter quantity may be uncertain by as much as 250 kJ·mol −1 , it shows, nevertheless, that the existence of S 2+ 8 in the solid state is the result of stabilization afforded by the greater molar crystal lattice energy of the 2-1 salt relative to that for twice the amount of substance of the 1-1 salt.…”

“…(1)(2)(3) For example, we have recently shown (3) that the cation S 2+ 8 in S 8 (AsF 6 ) 2 is stabilized in the solid state due to its high lattice energy, (1517 2 36) kJ·mol −1 , deduced from the standard molar enthalpy of formation D f H°m{S 8 (AsF 6 ) 2 } determined by fluorine bomb calorimetry, and ab initio calculations (4) of the energies of S 8 (g) and S 2+ 8 (g). In the gas phase, S …”

Thermodynamic properties of silicides IV. Determination of the standard molar enthalpies of formation at the temperature 298.15 K of pentatungsten trisilicides of composition W5Si3and W5Si3.115by fluorine-combustion calorimetry

“…(23) Detailed calorimetric information for the combustions in F 2 (g) is contained in tables 2 and 3, and the symbols used there have been explained. (4,5) Such auxiliary thermodynamic quantities as molar heat capacities of F 2 , WF 6 , SiF 4 , and SF 6 were the same as those used earlier.…”