The stabilities of gaseous germanium and tin vanadates were confirmed by high temperature mass spectrometry, and its structures were determined by quantum chemical calculations. A number of gas-phase reactions involving these gaseous salts were studied. On the basis of the equilibrium constants, the standard formation enthalpies of gaseous GeV₂O₆ (−1520 ± 42 kJ mol⁻¹) and SnV₂O₆ (−1520 ± 43 kJ mol⁻¹) were determined at a temperature of 298 K.