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

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

Research output: Contribution to journalArticle

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 languageEnglish
Pages (from-to)4106-4114
Number of pages9
JournalACS Catalysis
DOIs
Publication statusPublished - Jan 1 2019

Fingerprint

X ray absorption
Hydrogenation
Nanoparticles
Chemical activation
Ethers
X ray absorption fine structure spectroscopy
chlorambucil-arachidonic acid conjugate
Silver
Cations
Positive ions
Adsorption
Kinetics

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 journalArticle

Tran, Ba L. ; Fulton, John L. ; Linehan, John ; Balasubramanian, Mahalingam ; Lercher, Johannes A. ; Bullock, R Morris. / Operando XAFS Studies on Rh(CAAC)-Catalyzed Arene Hydrogenation. In: ACS Catalysis. 2019 ; pp. 4106-4114.
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