Abstract
The chemical behaviour of E-3-hexene on clean Ru(0 0 1) was studied by RAIRS, under UHV conditions, and compared to that of its geometrical isomer, Z-3-hexene. It is shown that, above 140 K, E-3-hexene dehydrogenates to 3-hexyne di-σ/π complex, which, by thermal activation above 170 K, undergoes C2–C3 and C4–C5 bond breaking, yielding ethylidyne (CCH3) and ethyne di-σ/π complex. However, while above ∼120 K the Z-isomer is completely decomposed, E-3-hexene is remarkably stable, since a significant fraction of physically adsorbed molecules remain on the Ru(0 0 1) surface up to 240 K. By direct adsorption at high temperatures (e.g. 220 K), the decomposition product detected by RAIRS is ethylidyne and, less clearly, the 3-hexyne di-σ/π complex, co-adsorbed with unreacted E-3-hexene. On the contrary, in the same adsorbing conditions, Z-3-hexene follows a second decomposition path involving CC bond scission, with formation of propylidyne and ethylidyne. These results highlight the importance of geometrical isomerism on the stability and decomposition paths of C6 alkenes on Ru(0 0 1), since it may modify the accessibility of the double bond.
Published Version
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