The chemical adsorption of 1-hexene on Ru(0001) studied by reflection-absorption infrared spectroscopy

The chemisorption of 1-hexene on a Ru(0001) surface has been studied using reflection-absorption infrared spectroscopy (RAIRS). At 92 K, a very low dose of 1-hexene produced a RAIR spectrum consistent with the formation of a di-σ type complex. On annealing to 100 K, this species started dehydrogenating on the surface, forming a mixture of rotational conformers of hexylidyne, [C(CH ₂) ₄CH ₃]. A similar result was obtained when adsorbing at 100 K, with predominance of the all-trans conformer of hexylidyne for exposure at a high rate. Hexylidyne proved to be stable up to at least 120 K, although the conformational equilibrium changed, gradually favouring species with gauche rotations. Between 130 and 290 K, the decomposition products did not produce detectable RAIR spectra. Further thermal decomposition into methylidyne was observed at 300 K, in contrast with shorter chain alkylidynes previously studied on Ru(0001), which decompose via ethylidyne.