In the present work, the stability of gaseous manganese-containing salts was proved by the high-temperature mass spectrometric method. New previously unreported species were found, MnPO₃ and MnPO₂. On the basis of equilibrium constants measured for gas-phase reactions the standard formation enthalpies for MnPO₃ and MnPO₂ were determined as -602.0 ± 10.0 kJ/mole and -299.0 ± 11.5 kJ/mole, respectively, and the standard atomization enthalpies as 1950 ± 14 kJ/mole and 1397 ± 14 kJ/mole, respectively.