Dissociation dynamics and thermochemistry of energy-selected CpCo(CO)(2)(+) ions

Photoelectron photoion coincidence (PEPICO) spectroscopy-has been used to i nvestigate the dissociation dynamics of the cyclopentadienyl cobalt dicarbo nyl ion;: CpCo(CO)(2)(+). The dissociation proceeds by the sequential loss of the two CO molecules. Both reactions proceed with no reverse activation energies and are slow near their dissociation onset. The 0 K onset was dete rmined by modeling the measured dissociation rate constants with RRKM theor y utilizing the variational transition state theory to locate the transitio n states. The ionization energy of CpCo(CO)(2) was measured from the thresh old photoelectron spectrum to be 7.35 eV, which agrees with the literature value; The neutral CpCo(CO)(2)(+): gas-phase heat of formation of -117 +/- 10 kJ/mol was determined from the liquid value by measuring the heat of vap orization of 52.12 +/- 0.68 kJ/mol. The first Co-CO bond energy in the CpCo (CO)(2)(+) was found to be 1.53 +/- 0.02 eV (148.1 +/- 2 kJ/mol), giving a 298 K gas phase heat of formation of 857 +/- 10 kJ/mol for CpCoCO+. The sec ond Co-CO bond energy in CpCoCO+ was measured to be 1.50 +/- 0.02 eV (144.8 +/- 2 kJ/mol), resulting in a 298 K gas phase heat of formation of CpCo+ t o be 1113 +/- 10 kJ/mol.