Reactivity and Structure of CF3I on Ru(001)

Abstract

A variety of surface-sensitive techniques are used to elucidate the reaction pathways, as well as adsorbate structures, associated with thermal activation of CF3J following adsorption on Ru(001) at 100 K. XPS shows that the C-I bond of CF3I dissociates below 200 K to form CF3(ad) and I(ad); the subsequent reactions of CF2 are best viewed as being regulated by the availability of surface sites. CF3(ad) dissociates to CF2(ad) below 200 K. Further CF3 dissociation, some of which is activated by H(ad), occurs between 200 and 400 K until all available sites are filled. Desorption of the remaining CF3, peaking at 705 K, once again opens surface sites for decomposition. This is followed by recombination of the products to form CF3(g). No evidence for CF(ad) is ever observed. Hydrogen coadsorption studies explain interesting features associated with fluorine evolution. HREELS and ESDIAD results indicate that CF3 adopts a tilted configuration on Ru(001).

An Electron-Stimulated Desorption Ion Angular Distribution and Low-Energy Electron Diffraction Investigation of CF3I on Ru(001)

“…A similar large hexagon is visible with the electron beam focused on the crystal edge, a photograph of which appears in ref . This pattern is visible at all CF 3 I exposures, appearing at 200 K for low exposures and at 400 K for exposures closer to, or exceeding, saturation.…”

“…The widespread use of fluorocarbons in technical applications has generated much interest in the chemistry of these molecules adsorbed on surfaces. In particular, the chemistry of trifluoroiodomethane (CF 3 I) adsorbed on metal surfaces has been the subject of several recent investigations. − The relatively weak C−I bond (2.3 eV) is easily cleaved thermally, making CF 3 I an ideal precursor for examining the reactivity of adsorbed trifluoromethyl groupsjust as a number of studies have successfully utilized iodoalkanes as precursors to adsorbed alkyl groups …”

“…Hence, a second study was undertaken to identify surface adsorbates, utilizing X-ray photoelectron spectroscopy (XPS), high resolution electron energy loss spectroscopy (HREELS), and H 2 coadsorption results, as well as preliminary ESDIAD data . The model which emerged from this study is summarized in Figure .…”

Catalysis for fluorination and trifluoromethylation

“…Trifluoromethyl groups are distinct from other alkyl groups such as the methyl (CH 3 ) group, both in terms of electronic structure and reactivity; the CF 3 group has the same electronegativity as chlorine (electronegativities: Cl, CF 3 = 3.2), and is similar in size to an isopropyl ( i -Pr) group (van der Waals radii: i -Pr, CF 3 = 2.2 Å) 48 . Trifluoromethyl groups, when bound to transition metals, can undergo side reactions, such as fluoride elimination 49,50 , that other alkyl groups cannot. Therefore, the trifluoromethyl group should be considered more appropriately as its own functional group rather than as a substituted methyl group.…”

Selective and Facile C−F Bond Activation of Trifluoromethyl Groups on Cu(111)

“…We are interested in such problems regarding controlled C−F activation of small fluorocarbons bound to metal surfaces. The chemistry of trifluoromethyl groups adsorbed on metal single-crystal surfaces was explored by the reactions of trifluoromethyl iodide (CF 3 I) with Ni, − Ru, , Pt , , and Ag …”