An Inelastic Electron-Tunneling Spectroscopic Investigation of the Reaction of Molybdenum Oxychlorides with a Hydroxylated Aluminum Oxide Surface

Article abstract of DOI:10.1021/ja00253a011

Molybdenum oxytetrachloride adsorbs on alumina at 22 deg C and reacts with the surface hydroxyl groups to form a dimeric oxydichloride-molybdenum complex.This complex desorbs slowly from the surface, as molybdenum dioxodichloride.Heating the surface during oxytetrachloride exposure yields poorly characterized decomposition products and tunnel junctions with very large conductivity changes as a function of bias voltage.Molybdenum dioxodichloride adsorbs on alumina at 22 deg C and forms an oligomerized molybdenum trioxide species.This oxide adsorbs water at a background pressure of approximately 1E-7 Torr, and it can be dehydrated by heating under vacuum to 100 deg C.Heating the surface during the vapor-phase exposure of molybdenum dioxodichloride, or the molybdenum oxide under vacuum after the exposure, increases the extent of polymerization.Exposure of the oxide to 2 Torr of ethylene at 100 deg C or 1E-1 Torr of acetic acid at 22 deg C produces changes in the tunneling spectra, due to increased oligomerization and some decomposition of the adsorbates, but there is no evidence for molecular adsorption or hydrocarbon formation.Exposure of the oxide to 5E-2 Torr of 4-tert-butylpyridine at 22 deg C causes the complete desorption of the oxide, presumably as the tripyridine complex.