Formation and stability of molybdenum-tellurium oxides MoTeO₅, Mo₂TeO₈, Mo₃TeO₁₁ and MoTe₂O₇ in the gas phase. Quantum chemical and mass spectrometry determination of standard enthalpy of formation

The formation of mixed molybdenum-tellurium oxides MoTeO₅, Mo₂TeO₈, Mo₃TeO₁₁, MoTe₂O₇ in the gas phase has been studied by mass spectrometry (MS) experiments at temperatures of about 938 K and studied theoretically by quantum chemical (QC) methods. Structural and thermodynamic data for the molecules was calculated. The mixed oxides MoTeO₅, Mo₂TeO₈, Mo₃TeO₁₁ and MoTe₂O₇ in the gas phase have been reported for the first time. Experimental thermodynamic data have been determined by means of MS and confirmed theoretically by DFT and ab initio (MP2) calculations. Adiabatic ionisation potentials (IPs) were obtained experimentally and compared with theoretical vertical ionisation potentials. The following values are given: Δ_fH⁰₂₉₈ (MoTeO₅) = −730.2 kJ mol⁻¹ (MS),Δ_fH⁰₂₉₈ (MoTeO₅) = −735.4 kJ mol⁻¹ (DFT), −717.3 kJ mol⁻¹ (MP2),S⁰₂₉₈ (MoTeO₅) = 389.5 J mol⁻¹ K⁻¹ (DFT),c_p⁰_T(MoTeO₅) = 141.71 + 13.54 × 10⁻³T − 2.53 × 10⁶T⁻² J mol⁻¹ K⁻¹ (298 < T < 940 K) (DFT),Δ_fH⁰₂₉₈ (Mo₂TeO₈) = −1436.3 kJ mol⁻¹ (MS),Δ_fH⁰₂₉₈ (Mo₂TeO₈) = −1436.1 kJ mol⁻¹ (DFT), −1455.9 kJ mol⁻¹ (MP2),S⁰₂₉₈ (Mo₂TeO₈) = 517.1 J mol⁻¹ K⁻¹ (DFT),c_p⁰_T(Mo₂TeO₈) = 228.64 + 24.15 × 10⁻³T − 4.09 × 10⁶T⁻² J mol⁻¹ K⁻¹ (298 < T < 940 K) (DFT),Δ_fH⁰₂₉₈ (Mo₃TeO₁₁) = −2132.7 kJ mol⁻¹ (MS),Δ_fH⁰₂₉₈ (Mo₃TeO₁₁) = −2110.7 kJ mol⁻¹ (DFT), −2163.2 kJ mol⁻¹ (MP2),S⁰₂₉₈ (Mo₃TeO₁₁) = 629.3 J mol⁻¹ K⁻¹ (DFT),c_p⁰_T(Mo₃TeO₁₁) = 316.40 + 34.10 × 10⁻³T − 5.74 × 10⁶T⁻² J mol⁻¹ K⁻¹ (298 < T < 940 K) (DFT),Δ_fH⁰₂₉₈ (MoTe₂O₇) = −999.7 kJ mol⁻¹ (MS),Δ_fH⁰₂₉₈ (MoTe₂O₇) = −1002.7 kJ mol⁻¹ (DFT), −1000.9 kJ mol⁻¹ (MP2),S⁰₂₉₈ (MoTe₂O₇) = 504.8 J mol⁻¹ K⁻¹ (DFT),c_p⁰_T(MoTe₂O₇) = 211.19 + 18.02 × 10⁻³T − 3.53 × 10⁶T⁻² J mol⁻¹ K⁻¹ (298 < T < 940 K) (DFT),IP(MoTeO₅) = 10.68 eV (DFT),IP(Mo₂TeO₈) = 10.4 ± 0.5 eV (MS), IP(Mo₂TeO₈) = 10.41 eV (DFT),IP(Mo₃TeO₁₁) = 10.7 ± 0.5 eV (MS), IP(Mo₃TeO₁₁) = 10.18 eV (DFT),IP(MoTe₂O₇) = 9.91 eV (DFT).