Chemistry of Cyclopropane on Pt(111): Thermal, Electron, and Photon Activation

Abstract

The thermal, electron, and photon-induced chemistry of cyclopropane, c-C3H6, adsorbed on Pt(111) at 100 K has been studied. The thermal chemistry is simple. Adsorption is saturable, no multilayer accumulates, and thermal desorption exhibits only c-C3H6 with one peak at 144 K. High-resolution electron energy loss spectra results indicate that c-C3H6 adsorbs with the plane of the ring tilted away from the surface normal. The electron-induced chemistry is more complex. Irradiation with 50 eV electrons activates dissociation of adsorbed c-C3H6 at 100 K, and there are thermally activated reactions during subsequent temperature-programmed desorption. The total cross-section for destruction of c-C3H6 is 8.2 (±0.2) × 10-17 cm2. For low electron fluences, <1016 cm-2, the chemistry involved is describable in terms of C−C bond breaking to open the ring and form metallacyclic species, some of which promptly lose H to form allylic (C3H5) moieties. In subsequent thermally activated reaction-limited processes, propylene...