TY - JOUR
T1 - Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation
AU - Tran, Ba L.
AU - Fulton, John L.
AU - Linehan, John C.
AU - Balasubramanian, Mahalingam
AU - Lercher, Johannes A.
AU - Bullock, R. Morris
N1 - Funding Information:
We thank the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences for support. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 and the Canadian Light Source and its funding partners.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/5/3
Y1 - 2019/5/3
N2 - 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 2 O 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 t Bu toward H 2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KO t Bu leads to the formation of a Rh-O t Bu complex that interferes with H 2 activation, precluding the formation of Rh nanoparticles. 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 are formed, however, benzothiophene binds irreversibly to the Rh nanoparticles, preventing the adsorption of H 2 and diphenyl ether for arene hydrogenation.
AB - 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 2 O 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 t Bu toward H 2 activation, which is a key step en route to Rh nanoparticles for arene hydrogenation. Excess KO t Bu leads to the formation of a Rh-O t Bu complex that interferes with H 2 activation, precluding the formation of Rh nanoparticles. 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 are formed, however, benzothiophene binds irreversibly to the Rh nanoparticles, preventing the adsorption of H 2 and diphenyl ether for arene hydrogenation.
KW - Rh(CAAC)
KW - arene hydrogenation
KW - benzothiophene poisoning
KW - cationic rhodium
KW - operando XAFS
KW - rhodium nanoparticles
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U2 - 10.1021/acscatal.8b04929
DO - 10.1021/acscatal.8b04929
M3 - Article
AN - SCOPUS:85064831100
VL - 9
SP - 4106
EP - 4114
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 5
ER -