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Title: Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation

Abstract

Rh K-edge X-ray absorption fine structure (XAFS) spectroscopy was used to examine the Rh-catalyzed arene hydrogenation of diphenyl ether by a combination of stoichiometric reactions of [(CAAC Cy,Dipp)Rh(COD)Cl] (Rh–Cl) (CAAC Cy,Dipp = cyclic alkyl amino carbene) and operando XAFS kinetics studies. Our results unequivocally show that Rh nanoparticles, generated from the single-site Rh complex Rh–Cl, catalyze the arene hydrogenation. Operando XAFS studies illuminate the role of silver cation on the precatalyst reactivity, the effect of increasing H 2 pressure on increasing the catalytic efficiency, the stabilizing influence of Ph 2O on the relative rate of formation of active Rh nanoparticles, and the absence of soluble single-site Rh species that might leach from bulk heterogeneous Rh nanoparticles. We gained insights into the divergent deactivation pathways mediated by substoichiometric benzothiophene and excess KO tBu toward H 2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KO tBu leads to the formation of a Rh–O tBu complex that interferes with H 2 activation, precluding the formation of Rh nanoparticles. Here, benzothiophene does not interfere with the activation of H 2 at Rh in the CAAC Cy,Dipp complex while Rh nanoparticles are formed. Once Rh nanoparticles aremore » formed, however, benzothiophene binds irreversibly to the Rh nanoparticles, preventing the adsorption of H 2 and diphenyl ether for arene hydrogenation.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1];  [2];  [1]; ORCiD logo [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1530417
Grant/Contract Number:  
[AC02-06CH11357]
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
[ Journal Volume: 9; Journal Issue: 5]; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Rh(CAAC); arene hydrogenation; benzothiophene poisoning; cationic rhodium; operando XAFS; rhodium nanoparticles

Citation Formats

Tran, Ba L., Fulton, John L., Linehan, John C., Balasubramanian, Mahalingam, Lercher, Johannes A., and Bullock, R. Morris. Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation. United States: N. p., 2019. Web. doi:10.1021/acscatal.8b04929.
Tran, Ba L., Fulton, John L., Linehan, John C., Balasubramanian, Mahalingam, Lercher, Johannes A., & Bullock, R. Morris. Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation. United States. doi:10.1021/acscatal.8b04929.
Tran, Ba L., Fulton, John L., Linehan, John C., Balasubramanian, Mahalingam, Lercher, Johannes A., and Bullock, R. Morris. Wed . "Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation". United States. doi:10.1021/acscatal.8b04929. https://www.osti.gov/servlets/purl/1530417.
@article{osti_1530417,
title = {Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation},
author = {Tran, Ba L. and Fulton, John L. and Linehan, John C. and Balasubramanian, Mahalingam and Lercher, Johannes A. and Bullock, R. Morris},
abstractNote = {Rh K-edge X-ray absorption fine structure (XAFS) spectroscopy was used to examine the Rh-catalyzed arene hydrogenation of diphenyl ether by a combination of stoichiometric reactions of [(CAACCy,Dipp)Rh(COD)Cl] (Rh–Cl) (CAACCy,Dipp = cyclic alkyl amino carbene) and operando XAFS kinetics studies. Our results unequivocally show that Rh nanoparticles, generated from the single-site Rh complex Rh–Cl, catalyze the arene hydrogenation. Operando XAFS studies illuminate the role of silver cation on the precatalyst reactivity, the effect of increasing H2 pressure on increasing the catalytic efficiency, the stabilizing influence of Ph2O on the relative rate of formation of active Rh nanoparticles, and the absence of soluble single-site Rh species that might leach from bulk heterogeneous Rh nanoparticles. We gained insights into the divergent deactivation pathways mediated by substoichiometric benzothiophene and excess KOtBu toward H2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KOtBu leads to the formation of a Rh–OtBu complex that interferes with H2 activation, precluding the formation of Rh nanoparticles. Here, benzothiophene does not interfere with the activation of H2 at Rh in the CAACCy,Dipp complex while Rh nanoparticles are formed. Once Rh nanoparticles are formed, however, benzothiophene binds irreversibly to the Rh nanoparticles, preventing the adsorption of H2 and diphenyl ether for arene hydrogenation.},
doi = {10.1021/acscatal.8b04929},
journal = {ACS Catalysis},
number = [5],
volume = [9],
place = {United States},
year = {2019},
month = {3}
}

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Works referencing / citing this record:

The debut of chiral cyclic (alkyl)(amino)carbenes (CAACs) in enantioselective catalysis
journal, January 2019

  • Pichon, Delphine; Soleilhavoup, Michele; Morvan, Jennifer
  • Chemical Science, Vol. 10, Issue 33
  • DOI: 10.1039/c9sc02810b