Abstract
A well-studied heterogeneous palladium(II) catalyst used for the cycloisomerization of acetylenic acids is known to be susceptible to deactivation through reduction. To gain a deeper understanding of this deactivation process and to enable the design of a reactivation strategy, in situ X-ray absorption spectroscopy (XAS) was used. With this technique, changes in the palladium oxidation state and coordination environment could be studied in close detail, which provided experimental evidence that the deactivation was primarily caused by triethylamine-promoted reduction of palladium(II) to metallic palladium nanoparticles. Furthermore, it was observed that the choice of the acetylenic acid substrate influenced the distribution between palladium(II) and palladium(0) species in the heterogeneous catalyst after the reaction. From the mechanistic insight gained through XAS, an improved catalytic protocol was developed that did not suffer from deactivation and allowed for more efficient recycling of the catalyst.
Original language | English (US) |
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Pages (from-to) | 2999-3008 |
Number of pages | 10 |
Journal | ACS Catalysis |
DOIs | |
State | Published - Feb 22 2021 |
Externally published | Yes |
Bibliographical note
KAUST Repository Item: Exported on 2021-03-01Acknowledgements: Financial support from the Swedish Research Council (2016-03897 and 2017-0432), the Berzelii Center EXSELENT, and the Knut and Alice Wallenberg Foundation (KAW 2016.0072) is gratefully acknowledged. We are also grateful for the allocation of beamtime at P64, PETRA III Extension, Deutsches Elektronen-Synchrotron (DESY), a member of the Helmholtz Association (HGF). We would like to thank Dr. Vadim Murzin and Dr. Wolfgang Caliebe for their assistance with using the P64 beamline. Another part of this research performed at the Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research and by the National Institutes of Health, National Institute of General Medical Sciences (including P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIGMS or NIH. We would also like to express our appreciation to Dr. Niclas Heidenreich, Dr. A. Ken Inge, and Dr. Sebastian Leubner for their assistance with the reactor. Dr. Oscar Verho would also like to acknowledge the Wenner-Gren Foundations Fellow Program for their support. Special thanks go to Dr. Samy Ould-Chikh from KAUST Catalysis Center for providing the Pd NP reference data, which was a very valuable help in the improvement of our manuscript.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.