The formation of epoxides from reactions of oxametallacycles on Ag(110): A density functional theory study
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abstract
Density functional theory (DFT) cluster calculations have been used to investigate the interaction of various oxametallacycle intermediates with the Ag(110) surface, with an emphasis on connecting oxametallacycle structure to the mechanism of olefin epoxidation. These studies indicate that two types of oxametallacycle structures may be formed on Ag(110): the OMME structure, which incorporates a silver dimer in the oxametallacycle ring, and the OME structure, which incorporates a single silver atom. Although OMME-type intermediates are calculated to be more thermodynamically stable for monofunctional epoxides (such as ethylene oxide), transition-state calculations suggest that OME oxametallacycles may be more likely structures along the reaction coordinate for olefin epoxidation. OME structures have also been identified as likely intermediates in the synthesis of multifunctional epoxide molecules such as 1-epoxy-3-butene (EpB). In these cases, the extra functional group can also bind to the surface to increase the heat of adsorption of the oxametallacycle intermediate. These calculations indicate that oxametallacycles may be important intermediates in silver-catalyzed epoxidation reactions and that differences in oxametallacycle stability may explain differences observed in the epoxidation kinetics of different olefins.
