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

Abstract

The Rh-catalyzed arene hydrogenation of diphenyl ether has been examined in detail by Rh K-edge X-ray absorption fine structure (XAFS) spectroscopy, using a combination of stoichiometric reactions of [(CAAC)Rh(COD)Cl] (Rh-Cl) (CAAC = cyclic alkyl amino carbene) and operando XAFS studies on the hydrogenations catalyzed by Rh nanoparticles generated from the single-site Rh complex, Rh-Cl. Operando XAFS studies illuminate the role of silver on pre-catalyst initiation, the effect of increasing H2 pressure on increasing catalytic efficiency, and 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 can leach from bulk heterogeneous Rh nanoparticles. We also gained insights into the divergent deactivation pathways mediated by sub-stoichiometric benzothiophene and excess KOtBu toward H2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KOtBu leads to formation of a Rh-OtBu complex that inhibits H2 activation and Rh nanoparticles are not formed. Benzothiophene does not interfere with the steps of H2 activation at the single-site Rh to form Rh nanoparticles; however, once Rh nanoparticles are formed benzothiophene interferes with catalytic activity by binding irreversibly to the Rh nanoparticles to prevent binding of H2 andmore » diphenyl ether to the Rh nanoparticles under our reaction conditions.« less

Authors:
 [1];  [1];  [1];  [2]; ORCiD logo [1]; ORCiD logo [1]
  1. BATTELLE (PACIFIC NW LAB)
  2. Argonne National Laboratory
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1530858
Report Number(s):
PNNL-SA-139703
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 9; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
catalysis, nanoparticles, hydrogenation

Citation Formats

Tran, Ba L., Fulton, John L., Linehan, John C., Balasubramanian, Mahalingam, Lercher, Johannes A., and Bullock, Ronald M. 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, Ronald M. 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, Ronald M. Fri . "Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation". United States. doi:10.1021/acscatal.8b04929.
@article{osti_1530858,
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, Ronald M.},
abstractNote = {The Rh-catalyzed arene hydrogenation of diphenyl ether has been examined in detail by Rh K-edge X-ray absorption fine structure (XAFS) spectroscopy, using a combination of stoichiometric reactions of [(CAAC)Rh(COD)Cl] (Rh-Cl) (CAAC = cyclic alkyl amino carbene) and operando XAFS studies on the hydrogenations catalyzed by Rh nanoparticles generated from the single-site Rh complex, Rh-Cl. Operando XAFS studies illuminate the role of silver on pre-catalyst initiation, the effect of increasing H2 pressure on increasing catalytic efficiency, and 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 can leach from bulk heterogeneous Rh nanoparticles. We also gained insights into the divergent deactivation pathways mediated by sub-stoichiometric benzothiophene and excess KOtBu toward H2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KOtBu leads to formation of a Rh-OtBu complex that inhibits H2 activation and Rh nanoparticles are not formed. Benzothiophene does not interfere with the steps of H2 activation at the single-site Rh to form Rh nanoparticles; however, once Rh nanoparticles are formed benzothiophene interferes with catalytic activity by binding irreversibly to the Rh nanoparticles to prevent binding of H2 and diphenyl ether to the Rh nanoparticles under our reaction conditions.},
doi = {10.1021/acscatal.8b04929},
journal = {ACS Catalysis},
number = 5,
volume = 9,
place = {United States},
year = {2019},
month = {5}
}