THE LOCAL-STRUCTURE OF ADSORBED METHYL THIOLATE - THE REACTIONS OF METHANETHIOL ON MO(110)

The reactions of methanethiol were studied on Mo(110) using temperature-programmed reaction, X-ray photoelectron, and high resolution electron energy loss spectroscopies. The S-H bond in methanethiol is broken upon adsorption to form a methyl thiolate intermediate at 100 K. The C-S bond of the intermediate is oriented along the surface normal based on vibrational data which indicates C3v symmetry since only one methyl rock mode is observed at 905 cm-1. Electron energy loss spectra also indicate that the C-S bond is weakened in the methyl thiolate intermediate compared to methanethiol. Methane is formed via C-S bond hydrogenolysis of the thiolate in a peak centered at 315 K; nonselective decomposition to atomic carbon and sulfur with gaseous dihydrogen is a competing process. Approximately 40% of the thiolate produces methane and the remaining 60% nonselectively decomposes. The kinetics and selectivity are related to the C-S bond strength in the thiolate and the lack of a stable gas-phase dehydrogenation product. The reactivity and structure of the thiolate is compared on Mo(110) and other metals.