The adsorption and reaction of 2-iodoethanol on Ag(111)

Oxametallacycles have been previously grafted onto Ag(110) by adsorbing 2-i odoethanol to mimic possible intermediates in the catalytic epoxidation of ethylene. Since Ag(111) has been shown to be a good model catalyst for this reaction under realistic pressures of ethylene and oxygen, this work was e xtended to studying the chemistry of 2-iodoethanol on Ag(111) using tempera ture-programmed desorption and reflection-absorption infrared spectroscopie s. It was found that iodoethanol reacts at relatively low temperatures to f orm 2-hydroxyethyl species and co-adsorbed iodine. Hydroxyethyl species rea ct above similar to 150 K to eliminate water and evolve equimolar amounts o f ethylene. The remaining fragment with stoichiometry C2H4O reacts with the surface to form predominantly oxametallacycles which thermally decompose a t similar to 260 K to yield acetaldehyde. A minority species is also identi fied which thermally decomposes to yield acetaldehyde at similar to 315 K a nd may be due to an oxametallacycle which adopts a different orientation as a function of temperature and coverage or a 2-hydroxyethylidene species. ( C) 2000 Elsevier Science B.V. All rights reserved.