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Title: Spectroscopic Characterization of $$μ$$-$$η$$1:$$η$$1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters

Abstract

Although oxygen is a common ligand in supported metal catalysts, its coordination has been challenging to elucidate. Herein we characterize a diiridium complex that has been previously shown by X-ray diffraction crystallography to incorporate a μ-η11-peroxo ligand. We observe markedly enhanced intensity at 788 cm-1 in the Raman spectrum of this complex, which is a consequence of bonding of the peroxo ligand but does not shift upon 18O labeling. Electronic structure calculations at the density functional theory level suggest that this increase in Raman intensity results from bands associated with rocking of CH2 substituents directly attached to P(Ph)2 groups coupling with the O-O band. These results provide part of the foundation for understanding oxygen ligands on a silica-supported tetrairidium carbonyl cluster stabilized with bulky electron-donating phosphine ligands [p-tert-butyl-calix[4]arene(OPr)3(OCH2PPh2) (Ph = phenyl; Pr = propyl)]. Reaction of the cluster with O2 also led to the growing in of a Raman band at 788 cm-1, similar to that in the diiridium complex and also assigned to the bonding of a bridging peroxo ligand. Infrared spectra recorded as the supported cluster reacted in sequential exposures to (i) H2, (ii) O2, (iii) H2, and (iv) CO indicate that two bridging peroxo ligands were bondedmore » irreversibly per tetrairidium cluster, replacing bridging carbonyl ligands without altering either the cluster frame or the phosphine ligands. X-ray absorption near edge and infrared spectra include isosbestic points signifying a stoichiometrically simple reaction of the cluster with O2, and mass spectra of the effluent gas show that CO2 formed by oxidation of one terminal CO ligand per cluster as H2 (and not H2O) formed, evidence that hydride ligands had been present on the cluster following treatment (i). The understanding of how O2 reacts with the metal polyhedron provides a foundation for understanding of how oxidation catalysis may proceed on the surfaces of noble metals.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [1]; ORCiD logo [2]
  1. Univ. of California, Davis, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Univ. of Alabama, Tuscaloosa, AL (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Molecular Foundry
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Chevron Corp.; German Research Foundation (DFG)
OSTI Identifier:
1580967
Grant/Contract Number:  
AC02-05CH11231; FG02-04ER15513; FG02-05ER15696
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 21; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Anions; Transition metals; Ligands; Cluster chemistry; Metal clusters

Citation Formats

Palermo, Andrew P., Schöttle, Christian, Zhang, Shengjie, Grosso-Giordano, Nicolás A., Okrut, Alexander, Dixon, David A., Frei, Heinz, Gates, Bruce C., and Katz, Alexander. Spectroscopic Characterization of $μ$-$η$1:$η$1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b01529.
Palermo, Andrew P., Schöttle, Christian, Zhang, Shengjie, Grosso-Giordano, Nicolás A., Okrut, Alexander, Dixon, David A., Frei, Heinz, Gates, Bruce C., & Katz, Alexander. Spectroscopic Characterization of $μ$-$η$1:$η$1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters. United States. https://doi.org/10.1021/acs.inorgchem.9b01529
Palermo, Andrew P., Schöttle, Christian, Zhang, Shengjie, Grosso-Giordano, Nicolás A., Okrut, Alexander, Dixon, David A., Frei, Heinz, Gates, Bruce C., and Katz, Alexander. Tue . "Spectroscopic Characterization of $μ$-$η$1:$η$1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters". United States. https://doi.org/10.1021/acs.inorgchem.9b01529. https://www.osti.gov/servlets/purl/1580967.
@article{osti_1580967,
title = {Spectroscopic Characterization of $μ$-$η$1:$η$1-Peroxo Ligands Formed by Reaction of Dioxygen with Electron-Rich Iridium Clusters},
author = {Palermo, Andrew P. and Schöttle, Christian and Zhang, Shengjie and Grosso-Giordano, Nicolás A. and Okrut, Alexander and Dixon, David A. and Frei, Heinz and Gates, Bruce C. and Katz, Alexander},
abstractNote = {Although oxygen is a common ligand in supported metal catalysts, its coordination has been challenging to elucidate. Herein we characterize a diiridium complex that has been previously shown by X-ray diffraction crystallography to incorporate a μ-η1:η1-peroxo ligand. We observe markedly enhanced intensity at 788 cm-1 in the Raman spectrum of this complex, which is a consequence of bonding of the peroxo ligand but does not shift upon 18O labeling. Electronic structure calculations at the density functional theory level suggest that this increase in Raman intensity results from bands associated with rocking of CH2 substituents directly attached to P(Ph)2 groups coupling with the O-O band. These results provide part of the foundation for understanding oxygen ligands on a silica-supported tetrairidium carbonyl cluster stabilized with bulky electron-donating phosphine ligands [p-tert-butyl-calix[4]arene(OPr)3(OCH2PPh2) (Ph = phenyl; Pr = propyl)]. Reaction of the cluster with O2 also led to the growing in of a Raman band at 788 cm-1, similar to that in the diiridium complex and also assigned to the bonding of a bridging peroxo ligand. Infrared spectra recorded as the supported cluster reacted in sequential exposures to (i) H2, (ii) O2, (iii) H2, and (iv) CO indicate that two bridging peroxo ligands were bonded irreversibly per tetrairidium cluster, replacing bridging carbonyl ligands without altering either the cluster frame or the phosphine ligands. X-ray absorption near edge and infrared spectra include isosbestic points signifying a stoichiometrically simple reaction of the cluster with O2, and mass spectra of the effluent gas show that CO2 formed by oxidation of one terminal CO ligand per cluster as H2 (and not H2O) formed, evidence that hydride ligands had been present on the cluster following treatment (i). The understanding of how O2 reacts with the metal polyhedron provides a foundation for understanding of how oxidation catalysis may proceed on the surfaces of noble metals.},
doi = {10.1021/acs.inorgchem.9b01529},
journal = {Inorganic Chemistry},
number = 21,
volume = 58,
place = {United States},
year = {2019},
month = {10}
}

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Figures / Tables:

Figure 1 Figure 1: Top panel: Schematic representation of the sequence of gas treatments used to characterize the bonding of oxygen to the supported Ir4 framework of 2. The horizontal arrows designate the gas to which the sample was exposed. The vertical arrows show the gases that were formed as products whenmore » the treatment gas was the one shown at the immediate left. Each treatment was performed in a flow system at 323 K and 1 bar as IR spectra of the solid sample were recorded and as the effluent gases were characterized by mass spectrometry. Bottom panel: Reaction of dioxygen with clusters C1 and C2 previously synthesized and characterized by single-crystal X-ray diffraction by Cowie et al.« less

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