Electron impact ionization of cobalt-tricarbonyl-nitrosyl, cyclopentadienyl-cobalt-dicarbonyl and biscyclopentadienyl-cobalt: appearance energies, bond energies and enthalpies of formation

Mass spectra of the title compounds on electron impact (EI) ionization, appearance energies and metastable ion decays are reported. Bond energies (D), as dissociation energies, and gas-phase enthalpies of formation (DeltaH(f)(o)) are derived from these data. Obtained DeltaH(f)(o) values are (-4.20 +/- 0.3) eV for Co(CO)(3)NO, (-0.92 +/- 0.3) eV for CpCo(CO)(2) (CP = C5H5 cyclopentadienyl) and (3.18 +/- 0.3) eV for Cp2Co. In neutral Co(CO)(3)NO, the (Co-NO) bond energy is 1.89 eV. In the cation, the mean bond energy (D-m) for (Co-NO)(+) is (1.74 +/- 0.35) eV. For carbonyl ligands the mean (Co-CO) bond energy amounts to 1.42 eV. In cations, the mean (Co-CO)(+) bond energy ranges from (1.34 +/- 0.61) eV in Co(CO)(3)NO to (1.35 +/- 0.05) eV in CpCo(CO)(2). For CpCo(CO)(2), D(Co-Cp) = 2.77 eV and D(Co-Cp)(+) = 3.70 eV are found. For neutral Cp2Co, dissociation energies of D(CpCo-Cp) = 3.54 eV and D(Co-Cp) = 2.77 eV are obtained for the sequential elimination of the first and the second Cp ligand, respectively. In Cp2Co+, D(CpCo-Cp)+ = 4.86 eV and D(Co-Cp)(+) = 3.98 eV are obtained, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.