skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy

Abstract

Supported mononuclear iridium complexes with ethene ligands were prepared by the reaction of Ir(C{sub 2}H{sub 4}){sub 2}(acac) (acac is CH{sub 3}COCHCOCH{sub 3}) with highly dehydroxylated MgO. Characterization of the supported species by extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopies showed that the resultant supported organometallic species were Ir(C{sub 2}H{sub 4}){sub 2}, formed by the dissociation of the acac ligand from Ir(C{sub 2}H{sub 4}){sub 2}(acac) and bonding of the Ir(C{sub 2}H{sub 4}){sub 2} species to the MgO surface. Direct evidence of the site-isolation of these mononuclear complexes was obtained by aberration-corrected scanning transmission electron microscopy (STEM); the images demonstrate the presence of the iridium complexes in the absence of any clusters. When the iridium complexes were probed with CO, the resulting IR spectra demonstrated the formation of Ir(CO){sub 2} complexes on the MgO surface. The breadth of the {nu}{sub CO} bands demonstrates a substantial variation in the metal-support bonding, consistent with the heterogeneity of the MgO surface; the STEM images are not sufficient to characterize this heterogeneity. The supported iridium complexes catalyzed ethene hydrogenation at room temperature and atmospheric pressure in a flow reactor, and EXAFS spectra indicated that the mononuclear iridium species remained intact. STEM images ofmore » the used catalyst confirmed that almost all of the iridium complexes remained intact, but this method was sensitive enough to detect a small degree of aggregation of the iridium on the support.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
Sponsoring Org.:
DOE - OFFICE OF SCIENCE
OSTI Identifier:
1019783
Report Number(s):
BNL-95629-2011-JA
Journal ID: ISSN 0021-9517; JCTLA5; TRN: US201116%%540
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis
Additional Journal Information:
Journal Volume: 269; Journal Issue: 2; Journal ID: ISSN 0021-9517
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ATMOSPHERIC PRESSURE; BONDING; CATALYSTS; DISSOCIATION; FINE STRUCTURE; HYDROGENATION; IRIDIUM; IRIDIUM COMPLEXES; SPECTRA; SPECTROSCOPY; TRANSMISSION ELECTRON MICROSCOPY; national synchrotron light source

Citation Formats

Uzun, A, Ortalan, V, Browning, N, and Gates, B. A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy. United States: N. p., 2010. Web. doi:10.1016/j.jcat.2009.11.017.
Uzun, A, Ortalan, V, Browning, N, & Gates, B. A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy. United States. https://doi.org/10.1016/j.jcat.2009.11.017
Uzun, A, Ortalan, V, Browning, N, and Gates, B. 2010. "A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy". United States. https://doi.org/10.1016/j.jcat.2009.11.017.
@article{osti_1019783,
title = {A Site-isolated Mononuclear Iridium Complex Catalyst Supported on MgO: Characterization by Spectroscopy and Aberration-corrected Scanning Transmission Electron Microscopy},
author = {Uzun, A and Ortalan, V and Browning, N and Gates, B},
abstractNote = {Supported mononuclear iridium complexes with ethene ligands were prepared by the reaction of Ir(C{sub 2}H{sub 4}){sub 2}(acac) (acac is CH{sub 3}COCHCOCH{sub 3}) with highly dehydroxylated MgO. Characterization of the supported species by extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopies showed that the resultant supported organometallic species were Ir(C{sub 2}H{sub 4}){sub 2}, formed by the dissociation of the acac ligand from Ir(C{sub 2}H{sub 4}){sub 2}(acac) and bonding of the Ir(C{sub 2}H{sub 4}){sub 2} species to the MgO surface. Direct evidence of the site-isolation of these mononuclear complexes was obtained by aberration-corrected scanning transmission electron microscopy (STEM); the images demonstrate the presence of the iridium complexes in the absence of any clusters. When the iridium complexes were probed with CO, the resulting IR spectra demonstrated the formation of Ir(CO){sub 2} complexes on the MgO surface. The breadth of the {nu}{sub CO} bands demonstrates a substantial variation in the metal-support bonding, consistent with the heterogeneity of the MgO surface; the STEM images are not sufficient to characterize this heterogeneity. The supported iridium complexes catalyzed ethene hydrogenation at room temperature and atmospheric pressure in a flow reactor, and EXAFS spectra indicated that the mononuclear iridium species remained intact. STEM images of the used catalyst confirmed that almost all of the iridium complexes remained intact, but this method was sensitive enough to detect a small degree of aggregation of the iridium on the support.},
doi = {10.1016/j.jcat.2009.11.017},
url = {https://www.osti.gov/biblio/1019783}, journal = {Journal of Catalysis},
issn = {0021-9517},
number = 2,
volume = 269,
place = {United States},
year = {2010},
month = {1}
}