Desulfurization of Saturated C3S Molecules on Mo(110): The Effect of Ring Strain

Article abstract of DOI:10.1021/ja00247a010

The reactions of trimethylene sulfide (c-C3H6S) and 1-propanethiol (C3H7SH) have been investigated on Mo(110) under ultrahigh vacuum using temperature-programmed reaction spectroscopy and Auger electron spectroscopy.Deuterium preadsorption experiments were conducted in conjunction with temperature-programmed reaction spectroscopy to deduce some mechanistic details of the reactions.Desulfurization reactions of both molecules to produce propane and peopene were observed in the temperature range of 300-350 K, with propane production preceding propene production.In addition, trimethylene sulfide decomposed to form cyclopropane at 190 K.Both trimethylene sulfide and 1-propanethiol reacted on Mo(110) to produce gaseous dihydrogen in two peaks at approximately 350 and 540 K, as well as surface carbon and sulfur.Small amounts of reversibly adsorbed 1-propanethiol desorbed from Mo(110) between 175 and 200 K.Auger electron spectroscopy measurements suggest that approximately 50percent of chemisorbed trimethylene sulfide decomposed to form hydrocarbons, while 70percent of irreversibly chemisorbed 1-propanethiol decomposed to form hydrocarbons.The decomposition of trimethylene sulfide to cyclopropane is postulated to occur by one of three pathways.One of these pathways is entirely intramolecular, and the other two involve metallacycle transition states or intermediates.Trimethylene sulfide and 1-propanethiol are proposed to form propane and propene by way of a surface propyl thiolate intermediate, in a fashion similar to the reactions of tetrahydrotiophene and 1-butanethiol on Mo(110).The possible contributions of ring strain to the energetics and selectivity of the desulfurization reactions are discussed.