Reactions of Ethoxysilanes with Silica: A Solid-State NMR Study

Behringer, Klaus D.; Blümel, Janet

doi:10.1080/10826079608015108

Cited by 51 publications

(52 citation statements)

References 27 publications

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“…The second coordinated COD is then replaced by CO to form 17 by bubbling carbon monoxide into the reaction mixture. [10,54] This route can be pursued under very mild conditions in organic solvents, and is therefore also suitable for phosphines containing an ethoxysilane group that might lead to side reactions [17] or crosslinking [16] otherwise. For phosphines with OH instead of SiOEt groups, such as 3 and 4, route 2 can be applied.…”

Section: Synthesis Of the Nickel Catalystsmentioning

confidence: 99%

“…For example, the support material best suited for the irreversible reaction with ethoxysilane groups is silica, while oxides like MgO, TiO 2 or acidic Al 2 O 3 lead to extensive and permanent linker leaching. [15] With silica, the different forms of leaching can be prevented efficiently by applying the right conditions concerning solvent [16] and temperature [17] during the immobilization step, and using rigorously dried silica. [16,18] As soon as there is one covalent Si-O-Si bond established, the linker is irreversibly bound.…”

Section: Introductionmentioning

confidence: 99%

“…[15] With silica, the different forms of leaching can be prevented efficiently by applying the right conditions concerning solvent [16] and temperature [17] during the immobilization step, and using rigorously dried silica. [16,18] As soon as there is one covalent Si-O-Si bond established, the linker is irreversibly bound. [15] Detachment of the metal fragment from the phosphine moieties [11,12] can be prevented by chelat-ing phosphines with ethoxysilane groups.…”

Section: Introductionmentioning

confidence: 99%

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New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

Reinhard¹,

Šoba²,

Röminger³

et al. 2003

Adv Synth Catal

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New dicarbonylnickel catalysts with a variety of mono-and bidentate phosphine ligands, such as Ph 2 P(CH 2 ) x PPh(CH 2 ) y Si(OEt) 3 (x 2, 3; y 2, 3), have been synthesized and fully characterized, three of them by X-ray analyses. All the catalysts have been immobilized on silica by reaction of the ethoxysilane or hydroxy groups of the phosphine linkers with the surface silanol groups. The clean immobilization was proved by 31 P solid-state NMR. It has been demonstrated that the C À O À Si bridge, in contrast to the strong Si À O À Si bond, is easily cleaved by organic solvents and water. With respect to the cyclotrimerization of phenylacetylene the optimal reaction conditions for all molecular and immobilized catalysts have been determined. Cyclooctane was the best solvent, and the optimal reaction temperature was 100 8C for reactions in homogeneous phase, and 155 8C for surface-bound catalysts. The bite angles and spacer lengths of the chelating ligands did not play a major role for the performance of the homogeneous or immobilized catalysts. The latter could be recycled for 12 times, with final substrate conversions still typically between 30 and 40%, and turnover numbers (TON) around 1500. With an excess of substrate in one run a TON of 4810 was obtained for an immobilized carbonylnickel complex with a dppp-type chelate phosphine (x 3, y 2). Reduction of the surface coverage generally resulted in catalysts with longer lifetimes, for example, reduction to one fourth gave a record TON of 7616 for this catalyst. The selectivities of the catalysts all followed one trend. The main products were the cyclotrimers 1,2,4-and 1,3,5-triphenylbenzene, besides dimers, linear trimers and tetramers as side-products. The fraction of the latter decreased at higher temperatures with homogeneous catalysts, and vanished entirely after a few cycles with the immobilized catalysts. On recycling, the initial ratio of unsymmetrical to symmetrical cyclotrimers of typically 5 : 1 gradually changed to about 1 : 1 for all catalysts.

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Section: Synthesis Of the Nickel Catalystsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

Reinhard¹,

Šoba²,

Röminger³

et al. 2003

Adv Synth Catal

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“…In contrast, the surface density of APTES molecules is not optimal when aromatic solvents such as toluene are used. 53 Therefore, the choice of organic solvent plays a critical step in silanization that can significantly affect a specific bioanalytical application.…”

mentioning

confidence: 99%

Immobilization of Antibodies and Enzymes on 3-Aminopropyltriethoxysilane-Functionalized Bioanalytical Platforms for Biosensors and Diagnostics

et al. 2014

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/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

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“…However, monopodal and/or bipodal anchoring becomes predominant 5) (vide infra) depending on the silanol density. Moreover, any residual alkoxy groups occasionally react with unreacted trialkoxysilanes to generate complicated species on silica 6) .…”

Section: Introductionmentioning

confidence: 99%

Immobilization of Molecular Catalysts on Silica <i>via</i> New Tripodal Linker Unit

Fukaya

2015

J. Jpn. Petrol. Inst.

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The design and synthesis of a new linker unit to enable uniform and robust immobilization of organic functional molecules onto silica supports is described. This linker unit can prevent leaching of grafted organic functional moieties from the support. The tripodal linker unit was applied to the preparation of mesoporous silica-immobilized amino-palladium and phosphino-palladium complex catalysts for the Suzuki-Miyaura coupling reaction of aryl bromides and aryl chlorides. Catalysts including the tripodal linker displayed better catalytic activities and less palladium leaching than catalysts including a conventional trialkoxy-type linker.

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Reactions of Ethoxysilanes with Silica: A Solid-State NMR Study

Cited by 51 publications

References 27 publications

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

Immobilization of Antibodies and Enzymes on 3-Aminopropyltriethoxysilane-Functionalized Bioanalytical Platforms for Biosensors and Diagnostics

Immobilization of Molecular Catalysts on Silica <i>via</i> New Tripodal Linker Unit

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