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 |
| DOIs | |
| Publication status | Published - Jan 1 2019 |
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Keywords
- arene hydrogenation
- benzothiophene poisoning
- cationic rhodium
- operando XAFS
- Rh(CAAC)
- rhodium nanoparticles
ASJC Scopus subject areas
- Catalysis
- Chemistry(all)
Cite this
Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation. / Tran, Ba L.; Fulton, John L.; Linehan, John; Balasubramanian, Mahalingam; Lercher, Johannes A.; Bullock, R Morris.
In: ACS Catalysis, 01.01.2019, p. 4106-4114.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation
AU - Tran, Ba L.
AU - Fulton, John L.
AU - Linehan, John
AU - Balasubramanian, Mahalingam
AU - Lercher, Johannes A.
AU - Bullock, R Morris
PY - 2019/1/1
Y1 - 2019/1/1
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
UR - http://www.scopus.com/inward/record.url?scp=85064831100&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85064831100&partnerID=8YFLogxK
U2 - 10.1021/acscatal.8b04929
DO - 10.1021/acscatal.8b04929
M3 - Article
AN - SCOPUS:85064831100
SP - 4106
EP - 4114
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
ER -