Strategies to Immobilize Well‐Defined Olefin Metathesis Catalysts: Supported Homogeneous Catalysis <i>vs.</i> Surface Organometallic Chemistry

Copéret, C.; Basset, J.‐M.

doi:10.1002/adsc.200600443

Cited by 213 publications

(100 citation statements)

References 130 publications

(107 reference statements)

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“…Immobilization allows simplification of the reaction procedure through better control of the process selectivity, easier separation of the catalyst from the reaction products, recyclability of expensive catalysts, good control of morphology of polymers, and high polymer bulk density [89][90][91][92]. For immobilization we selected inorganic mesoporous supports, e.g.…”

Section: Immobilized Schiff Base Ru Complexesmentioning

confidence: 99%

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Ding¹,

Sun²,

Monsaert³

et al. 2008

COS

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The paper presents recent work conducted in our group on the synthesis of a novel class of homogeneous and immobilized Rucomplexes containing Schiff bases as O,N-bidentate ligands benefiting from a versatile, quite general and thoroughly exemplified twostep procedure. The new Ru-complexes with improved stability incorporate a variety of Schiff bases, associated with traditional inorganic and organic ligands such as chloride, phosphanes, arenes, cyclodienes, NHC etc., and different carbenes (alkylidene, vinylidene, allenylidene and indenylidene). By a proper choice of the Schiff base, useful physical and chemical properties of the derived Rucomplexes could be induced resulting in tunable catalytic activity for metathesis and related processes. A pertinent example is the latency of selected Schiff base Ru catalysts which by becoming active only under specific conditions (heat or acid activation) are ideal for industrial applications, e.g. reaction injection molding processes. The synthetic approaches that are critically discussed in this artcile have led to a diversity of Ru-complexes of which several members have risen to the rank of commercial catalysts.

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Section: Immobilized Schiff Base Ru Complexesmentioning

confidence: 99%

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Ding¹,

Sun²,

Monsaert³

et al. 2008

COS

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“…Because of this, it would be desirable to heterogenize cinchona alkaloids by tethering (immobilizing, grafting) them on high-surface-area solid supports. Tethering (or anchoring) is in fact done often with organometallic catalysts [10,11], and has been extended recently to add functionality to typical catalyst supports such as silica or alumina [12,13]. New ''click'' chemistry [14] has been advanced to facilitate the attachment of molecular compounds or structures to surfaces, in one approach relying on the use of silylating reagents [12,15,16].…”

Section: Introductionmentioning

confidence: 99%

Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

2011

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Cinchonidine, a naturally occurring cinchona alkaloid, was tethered to a high-surface-area silica substrate in order to create a new solid chiral catalyst. Two synthetic routes were explored for this grafting, relying on the use of an intermediate linker and so-called ''click'' chemistry. Both routes proved viable, but the procedure where cinchonidine is first derivatized with 3-isocyanatopropyltriethoxysilane (ICPTEOS) at the alcohol position and the resulting product then anchored to the silica surface was deemed the most efficient. Bonding to the surface occurs via the formation of Si-O-Si bonds, on average two out of the three possible per cinchonidine, and takes place preferentially at silica surface sites with two geminal hydroxyl groups on the same silicon atom. Approximately 10% of the available OH surface groups are derivatized in this procedure. The resulting catalyst was successfully tested for the addition of aromatic thiols to unsaturated ketones, a reaction promoted by amines (the tertiary quinuclidine nitrogen atom in the case of cinchonidine). The activity of the supported cinchonidine proved comparable to that of the free molecule, but tethering does lead to a significant loss in enantioselectivity.

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“…The introduction of catalysts based on 1 – 3 , but predisposed for specific tasks, has further expanded the potential of olefin metathesis. For example, areas such as solid-supported catalysis,3 asymmetric olefin metathesis,4 tandem catalysis,5 living polymerization,1a,6 acyclic diene metathesis,7 and stereoselective cross-metathesis (CM) have each benefited from breakthroughs in catalyst design, development, and application 8…”

Section: Introductionmentioning

confidence: 99%

Cyclic Ruthenium-Alkylidene Catalysts for Ring-Expansion Metathesis Polymerization

et al. 2008

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A series of cyclic Ru-alkylidene catalysts have been prepared and evaluated for their efficiency in ring-expansion metathesis polymerization (REMP). The catalyst structures feature chelating tethers extending from one N-atom of an imidazolylidine ligand to the Ru metal center. The catalyst design is modular in nature, which provided access to Ru-complexes having varying tether lengths, as well as electronically different NHC ligands. Structural impacts of the tether length were unveiled through 1H NMR spectroscopy as well as single-crystal X-ray analyses. Catalyst activities were evaluated via polymerization of cyclooctene and key data are provided regarding propagation rates, intramolecular chain-transfer, and catalyst stabilities, three areas necessary for the efficient synthesis of cyclic poly(olefin)s via REMP. From these studies, it was determined that while increasing the tether length of the catalyst leads to enhanced rates of polymerization, shorter tethers were found to facilitate intramolecular chain-transfer and release of catalyst from the polymer. Electronic modification of the NHC via backbone saturation was found to enhance polymerization rates to a greater extent than did homologation of the tether. Overall, cyclic Ru-complexes bearing 5- or 6-carbon tethers and saturated NHC ligands were found to be readily synthesized, bench-stable, and highly active catalysts for REMP.

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Strategies to Immobilize Well‐Defined Olefin Metathesis Catalysts: Supported Homogeneous Catalysis vs. Surface Organometallic Chemistry

Cited by 213 publications

References 130 publications

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

Cinchona Alkaloids Tethered on Porous Silica as Enantioselective Heterogeneous Catalysts

Cyclic Ruthenium-Alkylidene Catalysts for Ring-Expansion Metathesis Polymerization

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