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Ir(CO)2(acac)] in the pores of N a Y zeolite was treated in CO and converted into [Ir4(CO)12]. The zeoliteencaged [Ir4(C0) 121 was characterized by infrared and extended X-ray absorption fine structure spectroscopies, with the data indicating a n average Ir-Ir coordination number of 2.6 and a n average Ir-Ir distance of 2.69 A, in agreement, within the experimental error, with the published crystallographic data for solid [Ir4(C0)12]. Structurally simple zeolite-encaged iridium clusters were made by decarbonylation of the [Ir4(CO)12] a t 325 O C in flowing He followed by Hz. The decarbonylated clusters had an average Ir-Ir coordination number of 3.4 and a bond distance of 2.70 A, consistent with the inference that the tetrahedral framework structure of [Ir4(C0) 121 had been retained after decarbonylation; thus, the cluster is represented as tetrahedral Ir4. Infrared spectra showed that [Ir4(CO)12] was re-formed when the sample was treated in CO at 60 O C .

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Ir(CO)~(acac)] in the pores of NaX zeolite was treated in CO and converted into indium carbonyl clusters, which are suggested on the basis of infrared spectra and comparisons with solution chemistry to be [HIr4(CO), I]-, which was subsequently converted into clusters that are suggested to be [Ir6(C0)15I2-. The former clusters in the NaX zeolite were decarbonylated by treatment in He followed by H2 at 573 K and characterized by extended X-ray absorption fine structure spectroscopy. The Ir-Ir first-shell coordination number (3.0) indicates that the clusters were predominantly Ir4 tetrahedra. The clusters postulated to be [Ir6(C0)15]2-were reversibly fragmented and reformed in the cages.