Gaseous metal silicides. II. Thermodynamic study of the molecules AuSi, Ausi2 and Au2Si with a mass spectrometer☆

Abstract The gaseous equilibria involving the molecules AuSi, AuSi 2 and Au 2 Si have been studied by means of the Knudsen effusion technique combined with mass spectrometric analysis of the vapor. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies (in kJ mole −1 ): D 0 0 [AuSi(g)] = 301.0 ± 6.0, D 0 0 [Au 2 Si(g)] = 582.7 ± 15 and D 0 0 [AuSi 2 (g)] = 602.1 ± 15. The corresponding D 0 298 values are: 305.2 ± 6.0, 589.1 ± 15 and 610.5 ± 15, and the standard heats of formation, Δ H 0 f,298 , 518.6, 602.9 and 668.9, respectively. Comparison of the atomization energies of these silicon—gold molecules with the literature values for the corresponding germanium—gold and tin—gold molecules indicates similarity in the nature of bonding.