Carl E. Brown

Branching ratios and bond dissociation energies from the excimer laser photolysis of group 6 metal carbonyls

Photolysis of the group 6 (Cr, Mo, W) metal carbonyls in the gas phase, at excimer laser wavelengths, may lead to more than one primary product. Branching ratios between these products have been measured as a function of photolysis wavelength, buffer gas pressure, and temperature using time‐resolved infrared spectroscopy. The results are modeled using a sequential dissociation mechanism in which branching ratios are determined by competition between unimolecular dissociation and collisional relaxation. The sensitivity of the results to thermochemical input parameters and assumptions concerning energy disposal mechanisms is discussed. Under qualified assumptions the branching ratio measurements provide estimates for CO bond dissociation energies for coordinatively unsaturated metal carbonyls. For Mo and W the individual bond dissociation energies are close to the average values but for Cr the first three ligands coordinated are significantly less strongly bound than the last three. This finding is discusse...

Interaction of alkanes with unsaturated metal centres: The complex W(CO)5C2H6 in the gas phase☆

Abstract The complex W(CO) 5 C 2 H 6 has been observed in the gas phase by time-resolved infrared spectroscopy following 308 nm laser photolysis of W(CO) 6 in the presence of C 2 H 6 . The complex is shown to be in equilibrium with its precursor, W(CO) 5 , at room temperature and to have a C 2 H 6 binding energy of 9.7±3 kcal mol −1 .

Association reactions of nickel atoms with carbon monoxide and alkenes at room temperature: binding energy of NiC2H4

Abstract We report a kinetic study of association reactions of nickel atoms with carbon monoxide, ethene, propene and 1-butene in carbon dioxide buffer gas in the pressure range 1–600 Torr at 296 K. RRKM theory is used together with results of previous ab initio electronic structure calculations to interpret association rate coefficients in terms of binding energies of 1:1 complexes. The binding energy of NiC 2 H 4 at 0 K is estimated as 35.5±5 kcal mol −1 . The role of excited electronic states of the complexes in the association reactions is briefly discussed.