Thermal stabilities of hexacarbonyl and subcarbonyls of molybdenum encapsulated in NaY and NaX zeolites

Decompositions of Mo(CO)6 and the resulting subcarbonyl species adsorbed on NaY and NaX zeolites have been investigated utilizing i.r., temperature-programmed decomposition and X.p.s. techniques. It was found that Mo(CO)6 encapsulated in the NaX zeolite was considerably less stable than that contained in the NaY zeolite, while intermediate subcarbonyl species, Mo(CO)3ads, showed a completely reversed thermal stability. The drastic difference in the stabilizing properties between X and Y zeolites is thought to result from the difference in the basic strength of the zeolite framework oxygen. The structure of Mo(CO)3ads is proposed on the basis of i.r. spectra. The X.p.s. results suggest that the adsorbed Mo(CO)3 species is decomposed to Mo-metal aggregates at 473 K.