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

Oxametallacycles have been previously grafted onto Ag(110) by adsorbing 2-iodoethanol 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 extended to studying the chemistry of 2-iodoethanol on Ag(111) using temperature-programmed desorption and reflection-absorption infrared spectroscopies. It was found that iodoethanol reacts at relatively low temperatures to form 2-hydroxyethyl species and co-adsorbed iodine. Hydroxyethyl species react above similar to 150 K to eliminate water and evolve equimolar amounts of ethylene. The remaining fragment with stoichiometry C2H4O reacts with the surface to form predominantly oxametallacycles which thermally decompose at similar to 260 K to yield acetaldehyde. A minority species is also identified which thermally decomposes to yield acetaldehyde at similar to 315 K and 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.