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In situ XAS study of the local structure and oxidation state evolution of palladium in a reduced graphene oxide supported Pd(ii) carbene complex during an undirected C-H acetoxylation reaction

Yuan, Ning ; Majeed, Maitham H. LU ; Bajnóczi, Éva G. ; Persson, Axel R. LU ; Wallenberg, L. Reine LU ; Inge, A. Ken ; Heidenreich, Niclas ; Stock, Norbert ; Zou, Xiaodong and Wendt, Ola F. LU , et al. (2019) In Catalysis Science and Technology 9(8). p.2025-2031
Abstract

In situ X-ray absorption spectroscopy (XAS) investigations have been performed to provide insights into the reaction mechanism of a palladium(ii) catalyzed undirected C-H acetoxylation reaction in the presence of an oxidant. A Pd(ii) N-heterocyclic carbene complex π-stacked onto reduced graphene oxide (rGO) was used as the catalyst. The Pd speciation during the catalytic process was examined by XAS, which revealed a possible mechanism over the course of the reaction. Pd(ii) complexes in the as-synthesized catalyst first go through a gradual ligand substitution where chloride ions bound to Pd(ii) are replaced by other ligands with a mean bond distance to Pd matching Pd-C/N/O. Parallel to this the mean oxidation state of Pd increases... (More)

In situ X-ray absorption spectroscopy (XAS) investigations have been performed to provide insights into the reaction mechanism of a palladium(ii) catalyzed undirected C-H acetoxylation reaction in the presence of an oxidant. A Pd(ii) N-heterocyclic carbene complex π-stacked onto reduced graphene oxide (rGO) was used as the catalyst. The Pd speciation during the catalytic process was examined by XAS, which revealed a possible mechanism over the course of the reaction. Pd(ii) complexes in the as-synthesized catalyst first go through a gradual ligand substitution where chloride ions bound to Pd(ii) are replaced by other ligands with a mean bond distance to Pd matching Pd-C/N/O. Parallel to this the mean oxidation state of Pd increases indicating the formation of Pd(iv) species. At a later stage, a fraction of the Pd complexes start to slowly transform into Pd nanoclusters. The mean average oxidation state of Pd decreases to the initial state at the end of the experiment which means that comparable amounts of Pd(0) and Pd(iv) are present. These observations from heterogeneous catalysis are in good agreement with its homogeneous analog and they support a Pd(ii)-Pd(iv)-Pd(ii) reaction mechanism.

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published
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Catalysis Science and Technology
volume
9
issue
8
pages
7 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85064616304
ISSN
2044-4753
DOI
10.1039/c8cy02430h
language
English
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yes
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74405d25-e83f-4e68-b71a-02566dc0bbd0
date added to LUP
2019-05-03 14:58:30
date last changed
2020-01-16 03:52:30
@article{74405d25-e83f-4e68-b71a-02566dc0bbd0,
  abstract     = {<p>In situ X-ray absorption spectroscopy (XAS) investigations have been performed to provide insights into the reaction mechanism of a palladium(ii) catalyzed undirected C-H acetoxylation reaction in the presence of an oxidant. A Pd(ii) N-heterocyclic carbene complex π-stacked onto reduced graphene oxide (rGO) was used as the catalyst. The Pd speciation during the catalytic process was examined by XAS, which revealed a possible mechanism over the course of the reaction. Pd(ii) complexes in the as-synthesized catalyst first go through a gradual ligand substitution where chloride ions bound to Pd(ii) are replaced by other ligands with a mean bond distance to Pd matching Pd-C/N/O. Parallel to this the mean oxidation state of Pd increases indicating the formation of Pd(iv) species. At a later stage, a fraction of the Pd complexes start to slowly transform into Pd nanoclusters. The mean average oxidation state of Pd decreases to the initial state at the end of the experiment which means that comparable amounts of Pd(0) and Pd(iv) are present. These observations from heterogeneous catalysis are in good agreement with its homogeneous analog and they support a Pd(ii)-Pd(iv)-Pd(ii) reaction mechanism.</p>},
  author       = {Yuan, Ning and Majeed, Maitham H. and Bajnóczi, Éva G. and Persson, Axel R. and Wallenberg, L. Reine and Inge, A. Ken and Heidenreich, Niclas and Stock, Norbert and Zou, Xiaodong and Wendt, Ola F. and Persson, Ingmar},
  issn         = {2044-4753},
  language     = {eng},
  number       = {8},
  pages        = {2025--2031},
  publisher    = {Royal Society of Chemistry},
  series       = {Catalysis Science and Technology},
  title        = {In situ XAS study of the local structure and oxidation state evolution of palladium in a reduced graphene oxide supported Pd(ii) carbene complex during an undirected C-H acetoxylation reaction},
  url          = {http://dx.doi.org/10.1039/c8cy02430h},
  doi          = {10.1039/c8cy02430h},
  volume       = {9},
  year         = {2019},
}