Dissociation Dynamics and Thermochemistry of Energy-Selected CpCo(CO)2+ Ions

Abstract

Photoelectron photoion coincidence (PEPICO) spectroscopy has been used to investigate the dissociation dynamics of the cyclopentadienyl cobalt dicarbonyl 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 determined by modeling the measured dissociation rate constants with RRKM theory utilizing the variational transition state theory to locate the transition states. The ionization energy of CpCo(CO)2 was measured from the threshold 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 vaporization 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...