S. Kawi

Reversible carbonylation/decarbonylation of zeolite-entrapped tetrairidium clusters

Iridium carbonyl clusters in NaY zeolite have been prepared from adsorbed [Ir(CO)2(acad)]. The infrared spectra and the yellow color of the sample are consistent with the formation of Ir4(CO)12] in the zeolite cages, presumably the product of reductive carbonylation of the mononuclear precursor. The iridium carbonyl cluster in the zeolite could be decarbonylated by treatment with flowing H2 at 300 ° C and 1 atm and recarbonylated by treatment with CO at 40 °C and 1 atm. The carbonylation/decarbonylation process is reversible, provided that the temperature of the decarbonylation is low, which suggests that the decarbonylated clusters may be Ir4. Treatment of the sample in H2 at 425 ° C and 1 atm led to the formation of particles or iridium metal outside the zeolite pores.

Hexairidium carbonyl clusters in the micropores of faujasite zeolites: evidence from transmission electron microscopy

Abstract[Ir6(CO)16] was formed in the pores of zeolite NaY by adsorption of [Ir(CO)2(acac)] followed by treatment in CO + H2. [Ir6(CO)15]2− in zeolite NaX was prepared similarly. Each sample was characterized by high‐resolution transmission electron microscopy. The images indicate the presence of the iridium clusters in the zeolite micropores, with almost no scattering centers indicating iridium outside these pores. The supported [Ir6(CO)16] and [Ir6(CO)15]2−, which have previously been characterized by infrared and extended X‐ray absorption fine structure spectroscopies, are among the most uniform and structurally best defined supported metal clusters.