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(f)H(298)(0) (MoTeO5) = −730.2 kJ mol(−1) (MS), Δ(f)H(298)(0) (MoTeO5) = −735.4 kJ mol(−1) (DFT), −717.3 kJ mol(−1) (MP2), S(298)(0) (MoTeO5) = 389.5 J mol(−1) K(−1) (DFT), c(p)(0)(T)(MoTeO5) = 141.71 + 13.54 × 10(−3)T − 2.53 × 10(6)T(−2) J mol(−1) K(−1) (298 < T < 940 K) (DFT), Δ(f)H(298)(0) (Mo2TeO8) = −1436.3 kJ mol(−1) (MS), Δ(f)H(298)(0) (Mo2TeO8) = −1436.1 kJ mol(−1) (DFT), −1455.9 kJ mol(−1) (MP2), S(298)(0) (Mo2TeO8) = 517.1 J mol(−1) K(−1) (DFT), c(p)(0)(T)(Mo2TeO8) = 228.64 + 24.15 × 10(−3)T − 4.09 × 10(6)T(−2) J mol(−1) K(−1) (298 < T < 940 K) (DFT), Δ(f)H(298)(0) (Mo3TeO11) = −2132.7 kJ mol(−1) (MS), Δ(f)H(298)(0) (Mo3TeO11) = −2110.7 kJ mol(−1) (DFT), −2163.2 kJ mol(−1) (MP2), S(298)(0) (Mo3TeO11) = 629.3 J mol(−1) K(−1) (DFT), c(p)(0)(T)(Mo3TeO11) = 316.40 + 34.10 × 10(−3)T − 5.74 × 10(6)T(−2) J mol(−1) K(−1) (298 < T < 940 K) (DFT), Δ(f)H(298)(0) (MoTe2O7) = −999.7 kJ mol(−1) (MS), Δ(f)H(298)(0) (MoTe2O7) = −1002.7 kJ mol(−1) (DFT), −1000.9 kJ mol(−1) (MP2), S(298)(0) (MoTe2O7) = 504.8 J mol(−1) K(−1) (DFT), c(p)(0)(T)(MoTe2O7) = 211.19 + 18.02 × 10(−3)T − 3.53 × 10(6)T(−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).