The coordination chemistry of methyl isocyanide (CH3NC), and CO are similar in a number of transition metal complexes, and it is therefore of interest to consider the surface chemistry of these molecules. We have used high resolution electron energy loss spectroscopy (EELS), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES) to characterize the interaction of CH3NC with Rh(111). At 120 K, EELS measurements indicate that CH3NC adsorbs nondissociatively as a bridged species. As the coverage is increased, vibrational loss features attributable to singly coordinated bonding occur, and multilayers of CH3NC eventually develop. In contrast, CO bonds initially to Rh in atop sites, with a bridged form occurring only at higher coverages. Thermally induced changes in the adsorbed CH3NC have also been monitored; TPD shows that H2, HCN, and N2are liberated from the surface between 350 and 850 K, and EELS has been used to follow the vibrational mode changes that accompany decomposition. Additional insight was provided by adsorbing CH3NC onto surfaces predosed with O2or CO, both of which produced some site blocking. Other interactional effects include CO and perhaps carbonate formation when CH3NC reacts with oxygen, and rapid removal of the intensity of the EELS modes associated with CO when CH3NC is adsorbed onto preadsorbed CO. Comparisons are made with previous results for CH3NC adsorption on Ni(111), Ag(311), and aluminahyphen;supported Rh clusters.
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