Trapping-mediated and multilayer-induced dissociative chemisorption of cyclobutane on Ru(001)

The dissociative chemisorption of cyclobutane on the Ru(001) surface has be en studied using thermal desorption spectroscopy (TDS) and high-resolution electron energy loss spectroscopy (HREELS). Two distinct methodologies have been used to study this reaction. First, we investigated the trapping-medi ated reaction by exposing the surface to cyclobutane at 180 K. Second, alth ough an adsorbed monolayer of cyclobutane undergoes nearly complete desorpt ion during subsequent heating, we find that the presence of the condensed m ultilayer induces significant reaction. Using HREELS we find that both reac tion channels yield a common intermediate which we identify to be a C4H8 me tallacycle. At moderate and high surface coverages, a small amount of buten e from the isomerization of the metallacycle desorbs between 185 and 225 K. Following the desorption of butene, we observe a hydrocarbon fragment on t he surface which is tentatively identified to be a C4H4 metallacycle.