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

Ba L. Tran; John L. Fulton; John C. Linehan; Mahalingam Balasubramanian; Johannes A. Lercher; R. Morris Bullock

doi:10.1021/acscatal.8b04929

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

Ba L. Tran, John L. Fulton, John C. Linehan, Mahalingam Balasubramanian, Johannes A. Lercher, R. Morris Bullock

Emerging and Solid-State Batteries

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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 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.

Original language	English
Pages (from-to)	4106-4114
Number of pages	9
Journal	ACS Catalysis
Volume	9
Issue number	5
DOIs	https://doi.org/10.1021/acscatal.8b04929
State	Published - May 3 2019

Funding

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.

Keywords

arene hydrogenation
benzothiophene poisoning
cationic rhodium
operando XAFS
Rh(CAAC)
rhodium nanoparticles

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10.1021/acscatal.8b04929

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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 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.",

keywords = "arene hydrogenation, benzothiophene poisoning, cationic rhodium, operando XAFS, Rh(CAAC), rhodium nanoparticles",

author = "Tran, {Ba L.} and Fulton, {John L.} and Linehan, {John C.} and Mahalingam Balasubramanian and Lercher, {Johannes A.} and Bullock, {R. Morris}",

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AU - Tran, Ba L.

AU - Fulton, John L.

AU - Linehan, John C.

AU - Balasubramanian, Mahalingam

AU - Lercher, Johannes A.

AU - Bullock, R. Morris

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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 - arene hydrogenation

KW - benzothiophene poisoning

KW - cationic rhodium

KW - operando XAFS

KW - Rh(CAAC)

KW - rhodium nanoparticles

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ER -

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

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