15min:

S. JASON DEE, VANESSA A. CASTLEBERRY, OTSMAR J. VILLARROEL, IVANNA E. LABOREN, SARAH E. FREY AND DARRIN J. BELLERT, Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798.

The construction of a custom fabricated photodissociation spectrometer permits the determination of thermodynamic properties (activation energies), reaction rates, and mechanistic details of bare metal cation mediated -bond activation in the gas phase. Specifically, the products and rates resulting from the unimolecular decomposition of the Ni⁺Acetaldehyde adduct are monitored after absorption of a known amount of energy. The two dissociative products which are observed in high yield are Ni⁺ and Ni⁺CO. The Ni⁺CO fragment ion could result from the activation of a C-C -bond or from the activation of a C-H -bond. The rate constant for the decarbonylation of Ni⁺Acetaldehyde was approximately 30 percent greater than that of the rate constant for the decarbonylation of Ni⁺Acetone. For the decarbonylation of Ni⁺Acetone, there needs to be a methide shift, whereas in the decarbonylation of Ni⁺Acetaldehyde one could have C-C insertion followed by an aldhyde H-shift. The rate-limiting step of the decarbonylation process will be discussed.