The Thermal Chemistry of Neopentyl Iodide on Ni(100) Surfaces: Selectivity between α-C−H and γ-C−H and between C−H and C−C Bond-Scission Steps in Chemisorbed Neopentyl Moieties

Abstract

The thermal chemistry of neopentyl iodide on Ni(100) single-crystal surfaces was characterized under vacuum by using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The first decomposition step, which takes place around 150 K, is the scission of the C−I bond, the same as in other chemisorbed alkyl halides. Owing to the absence of β hydrogens, however, no easy decomposition pathway is available for the resulting neopentyl surface species. Neopentane is produced via neopentyl reductive elimination with surface hydrogen, and desorbs in two stages around 140 and 180 K. The yield for this pathway is approximately 45% of the initial neopentyl iodide at saturation (which is approximately 0.2 ML) on the clean nickel, but reaches a value close to 100% if enough hydrogen (or deuterium) is predosed on the surface. The other major carbon-containing product from neopentyl iodide activation is isobutene, which desorbs around 400 K. Isotope labeling experiments demonstrated that the C...