Chemistry in cages. Zeolite-entrapped hexairidium cluster catalysts
- Univ. of Delaware, Newark (United States)
Iridium carbonyl clusters in the cages of NaY zeolite were prepared from adsorbed [Ir(CO)[sub 2](acac)]. Reductive carbonylation of this precursor in CO at 1 atm and 50[degrees]C gave [Ir[sub 4](CO)[sub 12]], which was converted in CO at 125[degrees]C and 1 atm to the isomer of [Ir[sub 6](CO)[sub 16]] with edge-bridging ligands and in CO + H[sub 2] at 250[degrees]C and 20 atm to the isomer of [Ir[sub 6](CO)[sub 16]] with face-bridging ligands, both identified by infrared and extended X-ray absorption fine structure (EXAFS) spectra. The zeolite containing the latter catalyzed the CO hydrogenation reaction at 20 atm and 250[degrees]C, giving a high selectivity to propane and being stable for a number of days in a flow reactor. Either isomer of [Ir[sub 6](CO)[sub 16]] in the zeolite could be decarbonylated in H[sub 2] at 300[degrees]C and 1 atm and recarbonylated to give either isomer of [Ir[sub 6](CO)[sub 16]]. The decarbonylated cluster in the presence of H[sub 2] is inferred from EXAFS spectra to be predominantly Ir[sub 6] with an octahedral structure and an average Ir-Ir bond distance of 2.71 A. These results illustrate the potential for preparation of supported metal clusters with controlled nuclearities and open the door to precise characterization of the structures and properties of uniform, highly dispersed supported metal catalysts. 82 refs., 11 figs., 5 tabs.
- DOE Contract Number:
- FG05-89ER45384; AC02-76CH00016
- OSTI ID:
- 6055617
- Journal Information:
- Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:11; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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100200* -- Synthetic Fuels-- Production-- (1990-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201 -- Chemical & Physicochemical Properties
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
CLATHRATES
COMPLEXES
DATA
ELEMENTS
EXPERIMENTAL DATA
HYDROGEN
HYDROGENATION
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IRIDIUM COMPLEXES
LIGANDS
MATERIALS
MINERALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SILICATE MINERALS
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
ZEOLITES