The adsorption of molybdenum hexacarbonyl on thin dehydroxylated alumina films grown on an Mo(100) single-crystal substrate is studied in ultrahigh vacuum using primarily temperature-programmed desorption and reflection-absorption infrared spectroscopy. Subcarbonyls are detected using infrared spectroscopy at low temperatures and desorb at similar to 245 K. A portion of the subcarbonyls decomposes to form an oxalate species on the surface, which thermally decomposes to evolve CO in two states at similar to 320 and 450 K. The coverage of the oxalate species is larger on dehydroxylated alumina than on hydroxylated or partially dehydroxylated alumina.