Electron Impact Ionization of Dicyclopentadienyl-Manganese and Cyclopentadienyl-Manganese-Tricarbonyl Compared with Dimanganese-Decacarbonyl: Appearance Energies,Bond Energies and Enthalpies of Formation

Abstract

Electron impact (EI) ionization mass spectra, metastable-ion decays and appearance energies are reported for the title compounds. Gas-phase formation enthalpies (ΔH_f) and bond energies (as dissociation energies) are derived from these data. Obtained ΔH_f values for the parent compounds are (–15.65 ± 0.2) eV for Mn₂(CO)₁₀, (2.85 ± 0.3) eV for Cp₂Mn (Cp = C₅H₅ = cyclopentadienyl ligand) and (–3.91 ± 0.3) eV for CpMn(CO)₃. The mean (Mn–CO) bond energy is 0.97 eV for Mn₂(CO)₁₀. In cations, the mean (Mn–CO)⁺ bond energy ranges from 0.75 to 0.80 eV for Mn₂(CO)₁₀ and CpMn(CO)₃, respectively. In Cp₂Mn⁺ the dissociation energies are 2.14 eV for the first Cp ligand and 3.21 eV for the second. In the neutral Cp₂Mn, 2.12 eV is needed for the detachment of a first Cp ligand and 3.00 eV for the second. The results for the second ligand are valid for the elimination of Cp from CpMn(CO)₃ as well.

Keywords

enthalpies of formation bond energies dissociation energies metastable ion decay mass spectra

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