Formation of iron clusters in zeolites of the faujasite-type X and Y by thermal decomposition of ironpentacarbonyl

The intercalation and thermal decomposition of Fe(CO)₅ in dehydrated zeolites of the faujasite-type X and Y is studied. The applied methods include chemical analysis, thermogravimetry, X-ray diffraction, electron microscopy, Mössbauer spectroscopy, and molecular-orbital cluster calculations. The decomposition of Fe(CO)₅ in X-zeolite (NaX) occurs stepwise at about 100°C and 200°C, while Fe(CO)₅ in Y-zeolite (NaY) decomposes continuously within a small temperature interval around 100°C. The decomposition products of NaX · Fe(CO)₅ are iron multimers, iron subcarbonyls, and ferrous high-spin iron depending on decomposition temperature and amount of intercalated Fe(CO)₅. The decomposition products of NaY · Fe(CO)₅ form α-Fe particles of considerable size (≈ 200 Å) probably outside the super-cages of NaY.