FIRST SYNTHESIS, EXPERIMENTAL AND THEORETICAL VIBRATIONAL-SPECTRA OF AN OXAMETALLACYCLE ON A METAL-SURFACE

High-resolution electron energy loss spectroscopy (HREELS) studies wer e performed to examine the reactions of 2-iodoethanol (ICH2CH2OH) on t he Ag(110) surface. The goal of these experiments was to isolate and s pectroscopically characterize a stable surface oxametallacycle, an int ermediate previously proposed but never isolated in the chemistry of a variety of oxygenates, including epoxides. The hydroxyethyl intermedi ate (-CH2CH2OH), formed from initial carbon-iodine bond scission, deco mposed at 263 K to yield a variety of volatile products as well as a s urface oxametallacycle (-CH2CH2O-). The oxametallacycle intermediate, formed at 263 K, remained intact until 340 K, permitting spectroscopic characterization by HREELS. Density Functional Theory (DFT) calculati ons were employed to determine the fully optimized structure for the o xametallacycle on silver and to predict the infrared spectrum and mole cular motions for that structure. The excellent agreement between the infrared spectrum predicted for an oxametallacycle incorporating two s ilver atoms and the experimental HREEL spectrum conclusively identifie s the surface oxametallacycle. The principal reaction channel for this intermediate in temperature programmed desorption (TPD) experiments i s coupling of two oxametallacycles to form the cyclic product gamma-bu tyrolactone, rather than the anticipated ring closure pathway to form ethylene oxide. However, one of the vibrational modes predicted by DFT appears to be a possible reaction coordinate for the conversion of ox ametallacycles to ethylene oxide.