{sup 129}Xe NMR spectroscopy of metal carbonyl clusters and metal clusters in zeolite NaY

[Ir{sub 4}(CO){sub 12}] and [Ir{sub 6}(CO){sub 16}] were synthesized in the pores of zeolite NaY by reductive carbonylation of sorbed [Ir(CO){sub 2}(acac)], and [Rh{sub 6}(CO){sub 16}] was similarly synthesized from [Rh(CO){sub 2}(acac)]. The supported metal carbonyl clusters were decarbonylated to...

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Bibliographic Details
Published in:Journal of the American Chemical Society 1999-08, Vol.121 (33)
Main Authors: Labouriau, A., Panjabi, G., Enderle, B., Peitrass, T., Gates, B.C., Earl, W.L., Ott, K.C.
Format: Article
Language:English
Subjects:
40 CHEMISTRY
CARBONYLS
ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
IRIDIUM
METALS
NUCLEAR MAGNETIC RESONANCE
XENON 129
ZEOLITES
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Summary:[Ir{sub 4}(CO){sub 12}] and [Ir{sub 6}(CO){sub 16}] were synthesized in the pores of zeolite NaY by reductive carbonylation of sorbed [Ir(CO){sub 2}(acac)], and [Rh{sub 6}(CO){sub 16}] was similarly synthesized from [Rh(CO){sub 2}(acac)]. The supported metal carbonyl clusters were decarbonylated to give supported clusters modeled on the basis of extended X-ray absorption fine structure spectra as Ir{sub 4}, Ir{sub 6}, and Rh{sub 6}, respectively. The supported metal carbonyl clusters and the supported metal clusters formed by their decarbonylation were investigated by {sup 129}XeNMR spectroscopy at temperatures in the range of 100--305 K. As the temperature increased, the chemical shift decreased. The curves representing the chemical shift as a function of temperature for xenon sorbed on the zeolite that contained clusters modeled as Ir{sub 4}, Ir{sub 6}, and Rh{sub 6} were all essentially the same and hardly different from that observed for the bare zeolite NaY. This comparison leads to the conclusion that xenon is less strongly adsorbed on the decarbonylated metal clusters than on the zeolite framework. Larger chemical shifts were observed for the zeolites containing the metal carbonyl clusters, with the largest being observed for the zeolite containing [Ir{sub 4}(CO){sup 12}]. These results are explained on the basis of the cluster sized and NaY zeolite geometry. The authors suggest that the contact between xenon and [Ir{sub 4}(CO){sub 12}] cluster is better than that between xenon and [Ir{sub 6}(CO){sub 16}] or xenon and [Rh{sub 6}(CO){sub 16}] clusters because these two larger clusters almost fill the zeolite supercages and exclude xenon, whereas [Ir{sub 4}(CO){sub 12}] in the supercages is small enough to allow entry of the xenon.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja990532j