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Titolo:
Synthesis and characterization of site-isolated hexarhodium clusters on titania powder
Autore:
Goellner, JF; Gates, BC;
Indirizzi:
Univ Calif Davis, Dept Chem Engn & Mat Sci, Livermore, CA 95616 USA Univ Calif Davis Livermore CA USA 95616 Mat Sci, Livermore, CA 95616 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 16, volume: 105, anno: 2001,
pagine: 3269 - 3281
SICI:
1520-6106(20010426)105:16<3269:SACOSH>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAY ABSORPTION-SPECTROSCOPY; FINE-STRUCTURE SPECTROSCOPY; METAL-SUPPORT INTERFACE; PROPYLENE HYDROFORMYLATION; CARBONYL CLUSTERS; ZEOLITE-Y; CATALYSTS; RHODIUM; ALUMINA; EXAFS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
46
Recensione:
Indirizzi per estratti:
Indirizzo: Gates, BC Univ Calif Davis, Dept Chem Engn & Mat Sci, Livermore, CA 95616 USA Univ Calif Davis Livermore CA USA 95616 Livermore, CA 95616 USA
Citazione:
J.F. Goellner e B.C. Gates, "Synthesis and characterization of site-isolated hexarhodium clusters on titania powder", J PHYS CH B, 105(16), 2001, pp. 3269-3281

Abstract

[Rh-6(CO)(16)] was prepared on the surface of TiO2 (calcined at 200 or 400degreesC) by deposition from n-hexane solution and by a surface-mediated synthesis from TiO2-supported [Rh(CO)(2)(acac)] in the presence of CO at 1 atm and 100 degreesC. The cluster preparation and subsequent decarbonylationby treatment in He or H-2 were characterized by infrared and extended X-ray absorption fine structure (EXAFS) spectroscopies. Deposition from solution gave aggregated [Rh-6(CO)(16)] on TiO2; removal of the carbonyl ligands led to destruction of the Rh-6 frame and sintering to give rhodium aggregates. In contrast, the reductive carbonylation of TiO2-supported [Rh(CO)(2)(acac)] gave site-isolated TiO2-supported [Rh-6(CO)(16)] in high yield, paralleling the chemistry of rhodium carbonyls in neutral solutions and on neutral surfaces. Removal of the carbonyl ligands from the site-isolated clustersby treatment in H-2 at 300 degreesC led to rhodium aggregates, but decarbonylation in He at 300 degreesC gave site-isolated Rh-6 clusters on the TiO2. The first-shell Rh-Rh coordination number of these clusters was 4.4 +/- 0.4 with a bond distance of 2.64 +/- 0.03 W. Thus, the clusters formed by decarbonylation of site-isolated TiO2-supported [Rh-6(CO)(16)] are represented as octahedral Rh-6 (which has a Rh-Rh first-shell coordination number of 4). EXAFS spectroscopy indicates that the decarbonylated Rh-6 clusters on TiO2 calcined at 200 degreesC have a small amount of carbon bonded to them, but no such ligands were indicated in the spectra of the Rh-6 clusters on TiO2 calcined at 400 degreesC.

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Documento generato il 21/09/20 alle ore 12:39:33