Are Heterogeneous Catalysts Precursors to Homogeneous Catalysts?

Davies, Ian W.; Matty, Louis; Hughes, David L.; Reider, Paul J.

doi:10.1021/ja016877v

Cited by 330 publications

(215 citation statements)

References 19 publications

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“…Leaching of catalytically active species from the supports was often a crucial problem generally. 92) In our case, however, the resulting filtrate separated from the reaction mixture had no catalytic activity under identical reaction conditions. Thus, it was confirmed that the catalytic activity observed was due to PdAS itself.…”

Section: Catalytic Activity Of Pdas For the Suzukimiyaura Reactionmentioning

confidence: 50%

Self-Assembled Complexes of Non-cross-linked Amphiphilic Polymeric Ligands with Inorganic Species: Highly Active and Reusable Solid-Phase Polymeric Catalysts

Yamada

2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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IntroductionDevelopment of immobilized and insoluble metal catalysts is of great interest in recent organic chemistry. [1][2][3][4][5][6][7][8][9] The simple recovery of catalysts by filtration and their reuses resulted in enhancing the economical evaluation of the reaction. At the same time, there is a prospect that the environmental pollution caused by residual metals in the waste fluid will be decreased. Although a great deal of effort has been made to carry out such ideal reactions using immobilized metal catalysts, what seems to be lacking is the efficiency of the catalytic systems. It is obvious that the heterogeneous catalytic systems exhibit generally lower activity than the homogeneous ones. Besides, it is expected that the activity of the catalysts decreases gradually in the recycled systems because the metal species leaches away from their supports. Taking these into consideration, we decided to concentrate on developing insoluble metal catalysts which are highly active and stable. We designed that they were still effective in the use of ppm mol eq, and in the recycled use of many times in any reaction media. To achieve the challenging theme, we have focused on the amphiphilic insoluble catalysts based on a novel concept (Chart 1).Over the past few decades, a considerable numbers of study have been made on solid-phase catalysts which were immobilized with cross-linked polystyrene resins, silica gels or metals. These catalytic systems, however, generally resulted in lower catalytic activity compared with their soluble counterparts, and were often obliged to use hazardous chlorohydrocarbon solvents. [10][11][12][13][14][15] Besides, reuse of these catalysts was often difficult owing to the gradual decline of the catalytic activity. These problems made them less practical.In traditional triphase catalysts, as I have mentioned before, a catalytic species was anchored to a linker that was immobilized to a polymer resin or silica gel (Chart 1, above). In July 2005Chem. Pharm. Bull. 53(7) 723-739 (2005)

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Section: Catalytic Activity Of Pdas For the Suzukimiyaura Reactionmentioning

confidence: 50%

Self-Assembled Complexes of Non-cross-linked Amphiphilic Polymeric Ligands with Inorganic Species: Highly Active and Reusable Solid-Phase Polymeric Catalysts

Yamada

2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…In a more rigorous test for the formation of a homogeneous species, a 3-phase test 47,48 was employed with Wang resin-bound substrate 14 (Figure 6a). In the presence of homogeneous PtCl 2 , 26% conversion of resin bound substrate to product was observed.…”

Section: Leaching Testsmentioning

confidence: 99%

“…The striking improvement in long-term activity of the smaller sized PAMAM dendrimer capped NPs over the larger PVP capped NPs is complemented by the differing recycling ability based on capping agent. Both results illustrate the effect of size and capping agent, which would not be possible if homogeneous catalysts were generated as the active species even if a "release and capture" dynamic were present.In a more rigorous test for the formation of a homogeneous species, a 3-phase test 47,48 was employed with Wang resin-bound substrate 14 (Figure 6a). In the presence of homogeneous PtCl 2 , 26% conversion of resin bound substrate to product was observed.…”

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Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles

et al. 2009

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A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl 2 , and catalyze a range of π-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues.The field of homogeneous catalysis can be characterized as a source of easily tuned, selective catalysts with high activity.Heterogeneous catalysts also offer many advantages, some of which are not displayed by their homogeneous counterparts, including recyclability, ease of separation from the reaction mixture and use in continuous flow processes. It is highly desirable to develop new systems that blend the many advantages of heterogeneous catalysis with the versatility of homogeneous catalysts. [1][2][3] Most efforts approach from the homogeneous side and are comprised of immobilized homogeneous catalyst species that promote reactions already accessible by homogeneous solution-state conditions. 1, 4 We sought to utilize an alternative method wherein heterogeneous catalysts are extended to reactions previously only catalyzed by homogeneous species. Metal nanoparticles (NPs) that serve as heterogeneous catalysts in which the metal particle size and oxidation state can be characterized are well-suited for our study. In addition, it is known that the reactivity and selectivity of monodisperse metal NPs can be altered by changes in their size and shape. [5][6][7][8][9][10][11][12][13][14][15] Although Pd and Au NPs have been demonstrated to catalyze a range of cross-coupling and oxidation/reduction reactions in solution, [16][17][18][19][20][21][22][23][24][25] studies have not yet yielded the control necessary to develop new NP catalysts applicable to a wider variety of reactions.A further challenge involves the specific nature of the catalyst. In particular, the distinction between homogeneous and heterogeneous catalysis is often difficult to determine. This is due to the possibility that metal leaches from a heterogeneous catalyst into solution and acts as the catalytically active species. Thus, it was important for us to consider in our studies the fact that for many of the...

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“…A more elegant example of the probable homogeneous nature of the reaction was provided by the use of a three phase test, originally applied to hydrogenations, 41 whereby one of the organic substrates is bound to a polymer resin so that only a homogeneous catalyst can diffuse to the reaction site. Grafting the aryl halide to a polymer does not affect the formation of product in the reaction (for Suzuki as well as Heck couplings), 42 although it has been pointed out that a potential shortcoming of this method is that it cannot distinguish between solution phase clusters small enough to diffuse efficiently and truly monometallic species. 34 In a carefully designed recent study by Rothenberg and co-workers a nanoporous alumina membrane (pore size < 11 nm) was used to demonstrate that large Pd clusters (> 11 nm) on one side of the membrane led to catalysis of the reaction on the other.…”

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confidence: 99%

Hydrogenation of benzene and toluene over size controlled Pt/SBA-15 catalysts: Elucidation of the Pt particle size effect on reaction kinetics

Пушкарев

Alayoǧlu

et al. 2012

Journal of Catalysis

123

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. (2012) 'Hydrogenation of benzene and toluene over size controlled Pt/SBA-15 catalysts : elucidation of the Pt particle size eect on reaction kinetics.', Journal of catalysis., 292 . pp. 64-72. Further information on publisher's website:http://dx.doi.org/10.1016/j.jcat.2012.04.022Publisher's copyright statement: This is the author's version of a work that was accepted for publication in Journal of Catalysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. A denitive version was subsequently published in Vladimir V. Pushkarev, Kwangjin An, Selim Alayoglu, Simon K. Beaumont, Gabor A. Somorjai (2012) Hydrogenation of benzene and toluene over size controlled Pt/SBA-15 catalysts: Elucidation of the Pt particle size eect on reaction kinetics, Journal of Catalysis, 292, pp. 64-72, http://dx.doi.org/10.1016/j.jcat.2012.04.022. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

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Are Heterogeneous Catalysts Precursors to Homogeneous Catalysts?

Cited by 330 publications

References 19 publications

Self-Assembled Complexes of Non-cross-linked Amphiphilic Polymeric Ligands with Inorganic Species: Highly Active and Reusable Solid-Phase Polymeric Catalysts

Self-Assembled Complexes of Non-cross-linked Amphiphilic Polymeric Ligands with Inorganic Species: Highly Active and Reusable Solid-Phase Polymeric Catalysts

Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles

Hydrogenation of benzene and toluene over size controlled Pt/SBA-15 catalysts: Elucidation of the Pt particle size effect on reaction kinetics

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