Carbon-carbon bond activation in the 1,2-ethanedioxy heterometallacycle by atomic oxygen on Ag(110)

Abstract

The effects of coadsorbed oxygen atoms on the decomposition of the 1,2-ethanedioxy surface species (OCH 2CH 2O (a)) formed during the partial oxidation of ethylene glycol (CH 2OH) 2 on the Ag(110) surface has been studied using temperature programmed reaction spectroscopy (TPRS), isotope labelling and high resolution electron energy loss vibrational spectroscopy (EELS). Surface oxygen atoms react with OCH 2CH 2O (a) at 300 K to form gaseous water and formaldehyde, and surface formate (HCOO (a)), which decomposes at 415 K to yield CO 2 and H 2. Through the use of isotopic labelling it was found that the oxygen in the formaldehyde originates solely from the 1,2-ethanedioxy surface species, while in the surface formate one comes from OCH 2CH 2O (a) and the other from coadsorbed oxygen atoms. The kinetic isotope effect for the reaction of adsorbed d 4-1,2-ethanedioxy with surface oxygen indicates that the rate limiting step is the abstraction of a proton from a methylene carbon in OCH 2CH 2O (a) to form OH a and OCHCH 2O (a). Nucleophilic attack by surface oxygen at the carbonyl carbon of OCHCH 2O (a), followed by C-C bond cleavage then releases H 2CO and forms HCOO (a). This study underscores the importance of looking at a wide range of concentrations of the pertinent surface species in order to probe a wider variety of reaction channels.