Neopentyl iodide on Pt(1 1 1) I. Adsorption and thermal decomposition

The chemistry of neopentyl iodide on Pt(1 1 1) single-crystal surfaces was characterized by temperature programmed desorption and reflection-absorption infrared spectroscopy. As with many other halo hydrocarbons, the first thermal reaction observed with neopentyl iodide on the platinum surface is the cleavage of the C–I bond, a step that leads to the formation of neopentyl surface species by 170 K. Hydrogenation of those intermediates is quite facile, taking place by 270 K and removing over 90% of the initial surface species. The remaining neopentyl groups undergo stepwise dehydrogenation to form a number of surface intermediates around 235 K, the identity of which is discussed in the following paper. The selectivity towards a given dehydrogenation reaction at that temperature depends on the regiospecificity of the deuterium labeling of the original molecule. Nevertheless, heating of any of those intermediates to 300 K leads to the formation of neopentylidyne. Small amounts of hydrogenolysis products are also detected at 300 and 430 K, presumably resulting from cracking of neopentylidene and neopentylidyne surface species, respectively.