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

Abstract

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 (Δ H° f) are derived from these data. Obtained Δ H° f values are (−4.20±0.3) eV for Co(CO) 3NO, (−0.92±0.3) eV for CpCo(CO) 2 (Cp=C 5H 5=cyclopentadienyl) and (3.18±0.3) eV for Cp 2Co. In neutral Co(CO) 3NO, 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) 3NO 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 Cp 2Co, 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 Cp 2Co +, D(CpCoCp) +=4.86 eV and D(CoCp) +=3.98 eV are obtained, respectively.