Tetrairidium clusters supported on [gamma]-Al[sub 2]O[sub 3]. Formation from [Ir[sub 4](CO)[sub 12]] and CO-induced morphology changes
- Univ. of Delaware, Newark (United States)
[Ir[sub 4](CO)[sub 12]] was prepared on the surface of [gamma]-Al[sub 2]O[sub 3] powder by a surface-mediated synthesis from supported [Ir(CO)[sub 2](acac)] in the presence of CO. Supported iridium clusters with nearly unique structures were prepared by decarbonylation of the iridium carbonyl clusters at 300[degrees]C in He. The cluster formation and decarbonylation were characterized by infrared and extended X-ray absorption fine structure spectroscopies. As the sample was heated in He to about 75[degrees]C, the infrared spectrum changed to resemble that of [HIr[sub 4](CO)[sub 11]][sup [minus]], which could be extracted from the surface by cation metathesis. The decarbonylation of this cluster took place without changes in the frequencies of the infrared bands in the carbonyl region, consistent with the suggestion that no other iridium carbonyls formed. The decarbonylated clusters in the presence of He had an average Ir-Ir coordination number of 2.9 with a bond distance of 2.69 A, indicating that the tetrahedral metal frame of the precursor cluster carbonyl had been largely retained after decarbonylation. Thus, the supported cluster is represented as Ir[sub 4] with a tetrahedral structure and is inferred to be one of the simplest and most uniform supported metals. When this sample was recarbonylated at 125[degrees]C, neither [Ir[sub 4](CO)[sub 12]] nor [HIr[sub 4](CO)[sub 11]][sup [minus]] was reformed. Instead, the recarbonylated clusters had an average Ir-Ir coordination number of 4.1 with an average bond distance of 2.70 A, indicating cluster agglomeration. 66 refs., 9 figs., 3 tabs.
- DOE Contract Number:
- FG05-89ER45384; AC02-76CH00016
- OSTI ID:
- 6258950
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CHALCOGENIDES
COMPLEXES
DATA
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
GASES
HELIUM
INFORMATION
IRIDIUM
IRIDIUM COMPLEXES
METALS
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
RARE GASES
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS