AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP5
C-C Bond Breaking in Cyclopropane on the Ni(411) Surface

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: A.J. Guikema, University of Michigan
Authors: A.J. Guikema, University of Michigan
J.L. Gland, University of Michigan
Correspondent: Click to Email
Thermal C-C bond breaking in cyclopropane has been observed on the stepped Ni(411) surface indicating that (111) step sites on a (100) terrace can break C-C bonds both in the presence and absence of coadsorbed hydrogen. Propane resulting from C-C bond activation in the presence of hydrogen is observed near 220 K. With increasing coverages of coadsorbed hydrogen and cyclopropane the yield of propane at 220 K increases. Above half saturation coverages of hydrogen and cyclopropane the yield of propane decreases with increasing coadsorbed coverages. The maximum propane yield corresponds to approximately 25% of cyclopropane saturation coverage. Experiments with coadsorbed deuterium clearly indicate that coadsorbed deuterium participates in propane formation. These observations support a Langmuir-Hinshelwood mechanism for propane formation associated with active sites in the step or near-step region. In the absence of coadsorbed hydrogen, cyclopropane dehydrogenation on the step sites dominates. A small amount of methane and ethane are observed around 120 K indicating multiple bond breaking during disproportionation. No deuterium incorporation is observed for methane and ethane in the presence of coadsorbed deuterium indicating that intermolecular hydrogen transfer dominates during disproportionation. These results indicate that the most reactive disproportionation sites responsible for multiple bond breaking react first and result in formation of about 5% of a monolayer of methane and ethane below 150 K.