Aryl iodides as strong inhibitors in gold and gold-based bimetallic quasi-homogeneous catalysis

Dhital, Raghu Nath; Kamonsatikul, Choavarit; Somsook, Ekasith; Sato, Yoshinori; Sakurai, Hidehiro

doi:10.1039/c3cc39019e

Cited by 21 publications

(21 citation statements)

References 22 publications

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“…Moreover, the bimetallic NC had a higher catalytic activity towards chloroarenes than the bromo equivalents (Scheme c). For example, a comparison of the observed reaction rates for the decay of chlorotoluene ( k C−Cl ) and bromotoluene ( k C−Brl ) showed that the value of k C−Cl (5.6×10 −2 h −1 ) was nearly three times that of k C−Brl (2.0×10 −2 h −1 ) . The significant differences in the rates of activation of C−Cl and C−Br showed an unprecedented halide dependence on the catalytic activity of bimetallic gold/palladium catalyst, otherwise the order of reactivity should be ArBr>ArCl.…”

Section: Resultsmentioning

confidence: 99%

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Dhital

Bobuatong

Ehara

et al. 2015

Chemistry An Asian Journal

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New catalytic activity of gold/palladium alloy nanoclusters (NCs) for carbon-halogen bond activation is demonstrated. In the case of an aryl chloride, the inclusion of gold in a bimetallic catalyst is indispensable to achieve the coupling reactions. Gold has the unique effect of stabilizing palladium, such that Pd(2+) leached from clusters by means of spillover of chloride during oxidative addition. The thus-formed spillover intermediate further reacts heterogeneously in both Ullmann and Suzuki-type coupling reactions through a new type of mechanism. In the case of an aryl bromide, Ullmann coupling occurs through the spillover of bromide, similar to that of aryl chloride. However, a significant fraction of palladium also leached, which diminished the Ullmann coupling activity of the aryl bromide and, as a result, the order of reactivity was ArCl>ArBr. With regard to the activation of the C-Br bond towards a Suzuki-type reaction, the inclusion of a higher gold content in gold/palladium clusters stabilized palladium to prevent the leaching of Pd(2+) from the clusters by means of spillover of bromide. The spillover intermediate reacts heterogeneously with PhB(OH)2, palladium-rich gold/palladium, or pure palladium clusters; the oxidative addition of ArBr favors the extraction of palladium from the clusters, yielding Pd(2+) intermediates. The extracted intermediates react homogenously (Pd(2+/)Pd(0) catalysis) with PhB(OH)2, which results in the higher selectivity of the cross-coupling product. An initial step to observe such unprecedented halide dependency, together with the dynamic behavior of palladium on the surface of gold is the oxidative addition of Ar-X. A detailed insight into the first oxidative addition process was also examined by quantum chemical calculations.

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Section: Resultsmentioning

confidence: 99%

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Dhital

Bobuatong

Ehara

et al. 2015

Chemistry An Asian Journal

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“…The second active site is the surface of Pd nanoparticles acting as a coupling site. It is well‐known that Pd nanoparticles were inactive for the Ullmann‐coupling of chloroarenes . However, Pd nanoparticles could be active for the Ullmann coupling when Pd nanoparticles were made smaller and impregnated on active supports such as La 2 O 3 .…”

Section: Resultsmentioning

confidence: 99%

“…The activation of carbon‐chlorine bond in the oxidative addition on Pd is generally difficult, compared to that of carbon‐bromine or carbon‐iodine due to the high dissociative energy of carbon‐chlorine bond. A success story of the activation of carbon‐chlorine in the Ullmann coupling of chloroarenes was reported by Sakurai and co‐workers by running the experiments in the presence of bimetallic AuPd alloy nanoclusters supported by poly( n ‐vinylpyrrolidone) (PVP) as a catalyst under ambient temperature . The unusual character of the bimetallic AuPd alloy nanoclusters, which exhibit a higher catalytic activity towards chloroarenes than bromoarenes and iodobenzene, is much more interesting.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd‐Supported Calcined Ferrocenated La₂O₃

Chumkaeo

Poonsawat

Meechai

et al. 2018

Applied Organom Chemis

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Novel palladium‐doped nanoparticles have been explored to serve as the first metal oxide‐derived heterogeneous catalyst for Ullmann reaction of chloroarenes under mild condition (34 °C). This heterogeneous catalyst exhibited high catalytic activity towards the Ullmann homocoupling of chloroarenes into a series of useful symmetrically biaryl products with good to excellent yields in the presence of ethanol and NaOH, thereby leading to green and economical Ullmann reaction. The produced nanoparticles were successfully characterized by various techniques including PXRD, XPS, HRTEM, SEM‐EDS, BET, TGA techniques, elemental mapping analysis and ICP‐OES. Interestingly, based on characterization and experimental data, a reasonable mechanism has been proposed. Also, the formation of aryl methyl ketone as a by‐product has been further confirmed by isotopic labelling experiments that the acetyl moiety is derived from ethanol. Moreover, the catalyst was stable and could be easily reused up to 5 times under atmospheric air without suffering significant loss in catalytic activity.

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“…In addition, 4-NO 2 iodobenzene can give the corresponding symmetrical products with a yield of 88.6% in 2 h (entry 11). However, Dhital et al 24,61 reported that Au-Pd alloy nanoclusters stabilized by PVP could efficiently catalyze the Ullmann coupling of chloroarenes but not for bromoarenes and iodide arenes, and aryl iodide was a stronger inhibitor by forming a stable complex with a gold component. Obviously, the asprepared PdAu/NCB catalysts are more stable and adaptable to different substrates.…”

Section: Ullmann Coupling Reactionmentioning

confidence: 99%

PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions

et al. 2019

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Aryl iodides as strong inhibitors in gold and gold-based bimetallic quasi-homogeneous catalysis

Cited by 21 publications

References 22 publications

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd‐Supported Calcined Ferrocenated La₂O₃

PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions

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Aryl iodides as strong inhibitors in gold and gold-based bimetallic quasi-homogeneous catalysis

Cited by 21 publications

References 22 publications

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd‐Supported Calcined Ferrocenated La2O3

PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions

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Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd‐Supported Calcined Ferrocenated La₂O₃