GAS-PHASE REACTIONS OF COPPER ATOMS - FORMATION OF CU(CO)2, CU(C2H2)2, AND CU(C2H4)2

A laser photolysis-laser fluorescence technique is used to investigate reactions of ground-state copper atoms with carbon monoxide, acetylene, and ethylene at 295 and 325 K in Ar buffer gas at total pressures in the range 50-600 Torr. Kinetic studies show that a sequential addition of at least two ligand molecules per copper atom occurs in all cases. The monoligand complexes are thermally unstable at 295 K and either redissociate or add a second ligand molecule to form stable diligand complexes. A simple kinetic model is used that allows the dissociation energies of the monoligand complexes to be estimated. We find DELTA-E-degrees-0 in the range 25 +/- 5 kJ mol-1 for all complexes. The analysis also provides estimates of strong-collision, low-pressure association rate constants for the first ligand addition reactions. Simplified unimolecular rate calculations using molecular constants from previous experimental and theoretical studies show that the experimentally determined rate constants and dissociation energies are mutually consistent.