Pd nanoparticle and molecular Pd2+ leaching pathways for a strongly acid versus strongly basic resin supported Pd nanoparticle catalyst in Suzuki coupling

[Display omitted] •The leaching behaviour and mechanisms are elucidated via combined data analysis.•A homogeneous-heterogeneous catalytic system prevails for both NP catalysts.•The leaching pathway critically depends on the resin functionality.•Phenylpalladium(II)hydroxide complexes are proposed as...

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Published in:Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 374; pp. 576 - 588
Main Authors: Van Vaerenbergh, Beau, Lauwaert, Jeroen, Thybaut, Joris W., Vermeir, Pieter, De Clercq, Jeriffa
Format: Journal Article
Language:English
Published: Elsevier B.V 15.10.2019
Subjects:
Ion exchange resins
Leaching mechanisms
Palladium nanoparticles
Supported nanoparticle catalysts
Suzuki-Miyaura cross-coupling reaction
Leaching mechanisms
Ion exchange resins
Supported nanoparticle catalysts
Suzuki-Miyaura cross-coupling reaction
Palladium nanoparticles
ISSN:1385-8947, 1873-3212
Online Access:Get full text
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Summary:[Display omitted] •The leaching behaviour and mechanisms are elucidated via combined data analysis.•A homogeneous-heterogeneous catalytic system prevails for both NP catalysts.•The leaching pathway critically depends on the resin functionality.•Phenylpalladium(II)hydroxide complexes are proposed as the leached Pd2+ species. The Pd leaching behaviour of a strongly acid (Lewatit K2629) versus strongly basic (Lewatit MP500 OH) ion exchange resin supported Pd nanoparticle (Pd-NP) catalyst is elucidated in the Suzuki reaction between iodobenzene and phenylboronic acid with K2CO3 as base in 1:1 (v/v) DMF/H2O at 40 °C. Reaction and leaching kinetic analyses combined with hot filtration tests indicated heterogeneous-homogeneous catalysis for both Pd-NP catalysts. More particularly, leaching experiments showed that for Pd-NP Lewatit K2629, Pd-NP as well as molecular Pd2+ leaching (as phenylpalladium(II)hydroxide complexes) occurred due to, respectively, the disturbance of the electrostatic NP stabilization by dissociated K2CO3 and reaction with iodobenzene and hydroxide. For Pd-NP Lewatit MP500 OH, however, molecular Pd2+ leaching induced by iodobenzene, dominates. Hence, the resin functionality determines the contribution of each leaching pathway. Furthermore, at high conversions, Pd re-deposition occurred due to the decreased amount of leaching inducing reagents causing enlarged NPs in the resin which leached less in subsequent runs.
ISSN:1385-8947
1873-3212
DOI:10.1016/j.cej.2019.05.197