Carbon-hydrogen bond activation in methane and tert-butoxide(ads) by oxygen chemisorbed on Ag(110). Molecular orbital theory

Activation of the CH bond in CH{sub 4} and t-BuO(ads) by H{sup {sm bullet}} transfer to O adsorbed on the Ag(110) surface has been studied by the atom-superposition and electron-delocalization molecular orbital theory. Both abstractions are found to proceed with a low-energy barrier because of the presence of low-lying empty Ag surface orbitals at the Fermi level. Transfer of an electron to the Fermi level alleviates the initial closed-shell repulsion between the CH {sigma}-bond electron pair and the surface O (which is formally O{sup 2{minus}}) lone-pair orbital that ultimately forms the OH {sigma} bond. It is concluded that surface O behaves like a radical anion O{sup {sm bullet}{minus}} or R{sub 3}O{sup {sm bullet}} in its ability to form a single bond. These calculations also suggest the possibility that surface oxygen atoms might insert into CH bonds to form alcohols, which is a result of their ability to exhibit O atom or carbene (R{sub 2}C:) bonding properties.