Carbon−Carbon Bond Activation in Adsorbed Cyclopropane by Gas-Phase Atomic Hydrogen on the Ni(111) Surface

Abstract

Gas-phase atomic hydrogen induces C-C bond activation in adsorbed cyclopropane on the Ni(111) surface, while coadsorbed hydrogen does not. Propane is the only desorbing product observed during subsequent temperature-programmed desorption experiments. Three propane formation pathways are observed. Gasphase atomic hydrogen reacts with adsorbed cyclopropane to form intermediates at 105 K, which are hydrogenated by coadsorbed hydrogen to form propane at 116 and 210 K. The 116 K pathway is similar to previous results obtained on the Ni(100) surface where propyl was determined to be the primary intermediate. The 210 K pathway has no analogue on the Ni(100) surface and is thought to involve a more stable form of propyl on the Ni(111) surface. The reaction of subsurface hydrogen with adsorbed cyclopropane leads to propane formation at 170 K on the Ni(111) surface. The absence of methane and ethane formation indicates that no multiple C-C bond activation processes occur. In contrast, cyclopropane desorption occurs before sufficient thermal energy is available to induce C-C bond breaking with coadsorbed hydrogen.

Interaction of gas phase atomic hydrogen with Pt(111): Direct evidence for the formation of bulk hydrogen species

“…Because gas phase atomic hydrogen is 218.4 kJ/mol more energetic than molecular hydrogen (1/2 dissociation energy of H 2 ), when interacting with Pt(111), gas phase atomic hydrogen is energetic enough to overcome any activation energy to form all likely adsorbed H ad species (surface H ad species and bulk H ad species), surely including the active species for practical catalytic reactions. Gland et al [21][22][23][24][25] found that gas phase atomic hydrogen can undergo ring-opening reaction directly with cycloalkanes adsorbed on metal single crystal surfaces and that the ring-opening reaction follows Eley-Rideal mechanism. Therefore, even under UHV conditions, interaction of gas phase atomic hydrogen with Pt(111) can lead to the formation of detectable bulk H ad species.…”