Styrene oxide undergoes an activated ring opening on Ag(111) at temperatures above 200 K. The product of this reaction is a stable oxametallacycle intermediate. The structure of this species has been obtained by density functional theory calculations and the computed vibrational spectrum is consistent with the experimental spectrum obtained using high-resolution electron energy loss spectroscopy. The oxametallacycle formed by ring-opening styrene oxide is structurally analogous to that previously observed for ring opening of epoxybutene on Ag(110) and represents the largest member of this adsorbate structure class yet isolated. In both cases, the epoxide ring opens at the carbon bearing the pendant unsaturated group, and the pendant group (phenyl in styrene oxide) is oriented nearly parallel to the surface plane. The oxametallacycle formed from styrene oxide reacts at 485 K to regenerate styrene oxide plus small amounts of phenylacetaldehyde. This peak temperature is similar to that previously reported for generation of styrene oxide from adsorbed styrene and oxygen atoms on Ag(111), suggesting that the epoxidation proceeds via the oxametallacycle intermediate isolated in the present work.

Synchrotron-based temperature-programmed X-ray photoelectron spectroscopy (TPXPS) in combination with temperature-programmed desorption (TPD) has been used to track C−Cl scission in the reaction of 1-chloro-2-methyl-2-propanol (Cl-tert-BuOH) on oxygen-containing Ag(110) surfaces. The results show that the oxygen pre-coverage strongly influences the cleavage of the C−Cl bond. At low coverages, C−Cl scission of chloro-t-butoxide intermediates begins at 200 K and isobutylene oxide (IBO) appears with a peak temperature of 235 K; at higher coverages, the onset of C−Cl scission is shifted upward by 50 K and the IBO peak by 80 K. Quantitative models for the surface reaction kinetics were developed from the experimental data. These show that the reaction of adsorbed intermediates does not occur by an SN2 process that releases IBO directly into the gas phase. Instead, C−Cl scission deposits organic intermediates or products on the surface, and the appearance of IBO in the gas-phase lags the appearance of atomic chlorine on the surface. For the lower temperature channel, the rate of IBO evolution in TPD is influenced by the kinetics of both C−Cl scission and molecular IBO desorption. At higher temperatures, surface diffusion processes to open surface sites limit the rate of IBO production. Comparison with results for chlorine diffusion into silver suggests that this is the relevant diffusion process.