- Latent ruthenium olefin metathesis catalysts featuring a phosphine or an N-heterocyclic carbene ligand
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The synthesis and characterization of latent 18-electron ruthenium benzylidene complexes (PCy3)((κN,O)-picolinate)2RuCHPh (5) and (H2IMes)((κN,O)-picolinate)2RuCHPh (6) are described. Both complexes appear as two isomers. The ratio between the isomers is dependent on l-type ligand. The complexes are inactive in ring-closing metathesis and ring-opening metathesis polymerization reactions even at elevated temperatures in the absence of stimuli. Upon addition of HCl, complexes 5 and 6 become highly active in olefin metathesis reactions. The advantage of the latent catalysts is demonstrated in the ring-opening metathesis polymerization of dicyclopentadiene, where the latency of 6 assures adequate mixing of catalyst and monomer before initiation. Trapping experiments suggests that the acid converts the 18-electron complexes into their corresponding highly olefin metathesis active 14-electron benzylidenes.
- Samec, Joseph S.M.,Keitz, Benjamin K.,Grubbs, Robert H.
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- Ionically tagged ru-alkylidenes for metathesis reactions under biphasic liquid-liquid conditions
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The synthesis of the novel ionic Ru-alkylidenes [Ru[(4-CO2)(1-CH3)Py+)]2(IMesH2)(=CH-2-(2-PrO)-C6H4)][OTf-]2 (1, IMesH2=1,3-dimesitylimidazolin-2
- Autenrieth, Benjamin,Willig, Felix,Pursley, Dominik,Naumann, Stefan,Buchmeiser, Michael R.
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- A practical larger scale preparation of second-generation hoveyda-type catalysts
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A two-step synthesis of the nitro-substituted Hoveyda-Grubbs olefin metathesis catalyst 4b from the parent first-generation Hoveyda-Grubbs complex 3a has been developed. The second-generation ruthenium catalyst was prepared by mixing together all ingredients, including a NHC ligand precursor and a strong base in an appropriate solvent. The formation of desired product 3b was separated from the liberated phosphine and decomposition products by flash chromatography using CH2Cl2 as the eluent. A good chelating 2-isopropoxybenzylidene fragment in 3b was replaced with the less chelating 5-nitro-2-isopropoxybenzylidene ligand. The resulting mixture was separated by crystallization from EtOAc from CH2Cl2 and finally from methanol. The method does not require extensive use of silica gel chromatography and can be easily scaled up.
- Bieniek, Michal,Michrowska, Anna,Gulajski, LUkasz,Grela, Karol
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- Insertion of imines into vinylcyclopropanes catalyzed by nucleophilic iron complexes: A formal [3+2]-cycloaddition strategy for the synthesis of substituted pyrrolidine derivatives
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Pyrrols are substructures in various biological active molecules. A straightforward iron-catalyzed synthesis of pyrrols via insertion of an imine into a vinylcyclopropane is presented. The corresponding pyrrols are obtained in moderate to good yields. Scope and limitations will be discussed.
- Pursley, Dominik,Plietker, Bernd
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- Reactivity and selectivity differences between catecholate and catechothiolate ru complexes. Implications regarding design of stereoselective olefin metathesis catalysts
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The origins of the unexpected finding that Ru catechothiolate complexes, in contrast to catecholate derivatives, promote exceptional Z-selective olefin metathesis reactions are elucidated. We show that species containing a catechothiolate ligand, unlike catecholates, preserve their structural integrity under commonly used reaction conditions. DFT calculations indicate that, whereas alkene coordination is the stereochemistry-determining step with catecholate complexes, it is through the metallacyclobutane formation that the identity of the major isomer is determined with catechothiolate systems. The present findings suggest that previous models for Z selectivity, largely based on steric differences, should be altered to incorporate electronic factors as well.
- Khan, R. Kashif M.,Torker, Sebastian,Hoveyda, Amir H.
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- Versatile Ru-based metathesis catalysts designed for both homogeneous and heterogeneous processes
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The synthesis of new ruthenium-based catalysts applicable for both homogeneous and heterogeneous metathesis is described. Starting from the Hoveyda-Grubbs first generation (1) and the Hoveyda-Grubbs second generation (2) catalysts the homogeneous catalysts [RuCl((RO)3Si-C3H6-N(R′)-CO-C3F6-COO)({double bond, long}CH-o-O-iPr-C6H4)(SIMes)] (4: R = Et, R′ = H; 5: R = R′ = Me) (SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) were prepared by substitution of one chloride ligand with trialkoxysilyl functionalized silver carboxylates (RO)3Si-C3H6-N(R′)-CO-C3F6-COOAg (3a: R = Et, R′ = H; 3b: R = R′ = Me). These homogeneous ruthenium-species are among a few known examples with mixed anionic ligands. Exchange of both chloride ligands afforded the catalysts [Ru((RO)3Si-C3H6-N(R′)-CO-C3F6-COO)({double bond, long}CH-o-O-iPr-C6H4)(SIMes)] (9: R = Et, R′ = H; 11: R = R′ = Me) and [Ru((RO)3Si-C3H6-N(R′)-CO-C3F6-COO)({double bond, long}CH-o-O-iPr-C6H4)(PCy3)] (8: R = Et, R′ = H; 10: R = R′ = Me). The reactivity of the new complexes was tested in homogeneous ring-closing metathesis (RCM) of N,N-diallyl-p-toluenesulfonamide and TONs of up to 5000 were achieved. Heterogeneous catalysts were obtained by reaction of 4, 5 and 8-11 with silica gel (SG-60). The resultant supported catalysts 4a, 5a, 8a-11a showed reduced activity compared to their homogenous analogues, but rival the activity of similar heterogeneous systems.
- Vehlow, Kati,Maechling, Simon,K?hler, Katrin,Blechert, Siegfried
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- High-Yield Synthesis of a Long-Sought, Labile Ru-NHC Complex and Its Application to the Concise Synthesis of Second-Generation Olefin Metathesis Catalysts
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The controlled reaction of [RuCl2(p-cymene)]2 with H2IMes generates the previously challenging precatalyst and Ru synthon RuCl2(p-cymene)(H2IMes) (Ru-2) in 96% isolated yield. Critical to success is inhibiting premature p-cymene displacement. This is achieved by carrying out the synthesis at ambient temperatures, protected from light, and at sufficient dilutions (25 mM in THF) to enable stoichiometric control and inhibit bimolecular decomposition. The ease with which p-cymene loss can be deliberately induced, however, is key to the utility of Ru-2 in both catalysis and catalyst synthesis. The transformation of Ru-2 into two second-generation olefin metathesis catalysts is described. RuCl2(H2IMes)(=CH(o-C6H4-OiPr)) (HII) and RuCl2(H2IMes)(PPh3)(=CHPh) GII′ (a desirable, faster-initiating analogue of GII) are accessible in ca. 80% yield over two steps from commercially available [RuCl2(p-cymene)]2. Synthesis from RuCl2(PPh3)3, in comparison, requires three or four steps for HII or GII′, respectively, and proceeds in lower yields.
- Day, Craig S.,Fogg, Deryn E.
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- Ruthenium Olefin Metathesis Catalysts Featuring a Labile Carbodicarbene Ligand
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Ruthenium benzylidene complexes containing a carbodicarbene (CDC) ligand are reported. Mechanistic studies indicate that the CDC ligand can dissociate under relatively mild conditions to afford active olefin metathesis catalysts. These catalysts were found to be effective at ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions.
- Liberman-Martin, Allegra L.,Grubbs, Robert H.
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- Light-Driven gem Hydrogenation: An Orthogonal Entry into “Second-Generation” Ruthenium Carbene Catalysts for Olefin Metathesis
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The newly discovered light-driven gem hydrogenation of alkynes opens an unconventional yet efficient entry into five-coordinate Grubbs-type ruthenium carbene complexes with cis-disposed chloride ligands. Representatives of this class featuring a chelate substructure formed by an iodo-substituted benzylidene unit react with (substituted) 2-isopropoxystyrene to give prototypical “second-generation” Grubbs-Hoveyda complexes for olefin metathesis. The new approach to this venerable catalyst family is safe and versatile as it uses a triple bond rather than phenyldiazomethane as the ultimate carbene source and does not require any sacrificial phosphines.
- Zachmann, Raphael J.,Fürstner, Alois
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- Synthesis and Evaluation of Ruthenium 2-Alkyl-6-mercaptophenolate Catalysts for Olefin Metathesis
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A series of ruthenium carbene catalysts containing 2-sulfidophenolate bidentate ligand with an ortho-substituent next to the oxygen atom were synthesized. The molecular structure of ruthenium carbene complex containing 2-isopropyl-6-sulfidophenolate ligand was confirmed through single crystal X-ray diffraction. An oxygen atom can be found in the opposite position of the N-heterocyclic carbene (NHC) based on the steric hindrance and strong trans-effects of the NHC ligand. The ruthenium carbene catalyst can catalyze ring-opening metathesis polymerization (ROMP) reaction of norbornene with high activity and Z-selectivity and cross metathesis (CM) reactions of terminal alkenes with (Z)-but-2-ene-1,4-diol to give Z-olefin products (Z/E ratios, 70:30–89:11) in low yields (13%–38%). When AlCl3 was added into the CM reactions, yields (51%–88%) were considerably improved and process becomes highly selective for E-olefin products (E/Z ratios, 79:21–96:4). Similar to other ruthenium carbene catalysts, these new complexes can tolerate different functional groups.
- Wang, Tao,Yu, Xiaobo,Zhang, Huiqing,Wu, Shutao,Guo, Weijie,Wang, Jianhui
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- Activation of olefin metathesis complexes containing unsymmetrical unsaturated N-heterocyclic carbenes by copper and gold transmetalation
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The activation of ruthenium-indenylidene complexes containing two unsymmetrical unsaturated N-heterocyclic carbenes (u2-NHCs) by a transmetalation process is reported. The use of copper(i) or gold(i) chlorides promotes the rapid trapping of one NHC ligand, which releases the catalytically active Ru-species. Impressive initiation rates with full-conversions are observed within one minute. This practical protocol demonstrates excellent catalytic performances in various ring-closing metathesis (RCM) and self-metathesis (SM) reactions.
- Kamal, Fadwa,Colombel-Rouen, Sophie,Dumas, Adrien,Guégan, Jean-Paul,Roisnel, Thierry,Dorcet, Vincent,Baslé, Olivier,Rouen, Mathieu,Mauduit, Marc
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supporting information
p. 11583 - 11586
(2019/10/02)
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- Cis-Dichloro Sulfoxide Ligated Ruthenium Metathesis Precatalysts
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Novel sulfoxide-ligated ruthenium complexes were prepared by reacting second-generation metathesis precatalysts with p-toluenesulfonyl chloride in the presence of a small excess of sulfoxide. (SIMes)Ru(S-DMSO)(Ind)Cl2 (M54) and (SIMes)Ru(S-DMSO)(CHPh)Cl2 (M54a) were characterized crystallographically and, in agreement with NMR spectroscopy, were found to adopt an unusual cis-dichloro configuration. Despite having traditionally latent geometry, the new complexes were found to be highly reactive precatalysts for routine metathesis transformations. Additionally, the robustness, scalability, and industrial utility of M54 as a ruthenium synthon are demonstrated.
- Johns, Adam M.,Fiamengo, Bryan A.,Herron, Jessica R.,Bourg, Jean-Baptiste,Doppiu, Angelino,Karch, Ralf,Pederson, Richard L.
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supporting information
p. 218 - 222
(2019/01/14)
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- A Gentler Touch: Synthesis of Modern Ruthenium Olefin Metathesis Catalysts Sustained by Mechanical Force
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Mechanochemical synthesis of nine contemporary ruthenium catalysts used for olefin metathesis is described, being the first reported example of formation of Ru carbene organometallic complexes in solid state. Three key organometallic transformations commonly used in the synthesis of the second and third generations of Ru catalysts in solution—phosphine ligand (PCy3) exchange with in situ formed N-heterocyclic carbene (NHC) ligand, PCy3 to pyridine ligand replacement, and benzylidene ligands interchange—were proved to work under mechanochemical conditions, affording the targets in high purity. Mechanochemical approach not only requires less amounts of organic solvent (null for synthesis, only for purification) and is scalable, but also allows for transformations that were reported impossible in the solution phase.
- Mukherjee, Nirmalya,Marczyk, Anna,Szczepaniak, Grzegorz,Sytniczuk, Adrian,Kajetanowicz, Anna,Grela, Karol
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p. 5362 - 5369
(2019/11/11)
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- Ruthenium complex, preparation method and application thereof
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The invention discloses a ruthenium complex, a preparation method and application thereof. The ruthenium complex disclosed in the invention is as shown in formula I. The ruthenium complex has good catalytic activity and stereoselectivity, provides various optimization options for catalytic cyclization of various olefin raw materials, can be used for industrial production of a catalyst for variousolefin metathesis translocation decomposition, and has a good application value.
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Paragraph 0153-0157; 0160-0166
(2019/01/23)
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- SYNTHESIS AND CHARACTERIZATION OF RU ALKYLIDENE COMPLEXES
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This invention relates generally to olefin metathesis catalyst compounds, to the preparation of such compounds, compositions comprising such compounds, methods of using such compounds, articles of manufacture comprising such compounds, and the use of such compounds in the metathesis of olefins and olefin compounds. The invention has utility in the fields of catalysts, organic synthesis, polymer chemistry, and industrial and fine chemicals industry.
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- Merrifield resin-assisted routes to second-generation catalysts for olefin metathesis
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Phosphine-scavenging resins can significantly facilitate the synthesis of highly active Ru metathesis catalysts, including the second-generation Grubbs, Hoveyda, and indenylidene catalysts (GII, HII, InII). These catalysts are customarily prepared by ligand exchange of the corresponding first-generation catalysts with the N-heterocyclic carbene (NHC) H2IMes. The PCy3 coproduct is conventionally removed by pentane extraction, but the partial solubility of the desired Ru products can cause product losses of over 20%. Sequestration of the PCy3 coproduct with CuCl is more efficient, but is undesirable given the potential for non-innocent copper residues. Use of the arylsulfonic acid resin Amberlyst-15 delivers near-quantitative catalyst yields, but the high acidity of the resin leads to problems with reproducibility and decomposition. An alternative approach is described, in which a neutral Merrifield resin (crosslinked polystyrene with pendant p-C6H4CH2I groups; MF-I) is used to sequester PCy3 as the covalently-tethered benzylphosphonium salt. Addition of MF-I following complete ligand exchange effects quantitative uptake of free PCy3 (and any residual free NHC) within 45 min at RT: the clean products are isolated by filtration, in ca. 95% yield. These yields compare well with those obtained via the Amberlyst-15 route, without the challenges due to resin acidity. The efficacy of this methodology is demonstrated in the synthesis of isotopically-labelled derivatives of HII, in which the H2IMes ligand bears a 13C-label at the carbene carbon, or perdeuterated mesityl rings.
- Nascimento, Daniel L.,Davy, Emma C.,Fogg, Deryn E.
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p. 1535 - 1544
(2018/03/28)
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- SYNTHESIS AND CHARACTERIZATION OF METATHESIS CATALYSTS
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This invention relates generally to olefin metathesis catalysts, to the preparation of such compounds, compositions comprising such compounds, methods of using such compounds, and the use of such compounds in the metathesis of olefins and in the synthesis of related olefin metathesis catalysts. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and in industrial applications such as oil and gas, fine chemicals, and pharmaceuticals.
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- METATHESIS CATALYSTS
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This invention relates generally to olefin metathesis catalysts, to the preparation of such compounds, compositions comprising such compounds, methods of using such compounds, and the use of such compounds in the metathesis of olefins and in the synthesis of related olefin metathesis catalysts. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and in industrial applications such as oil and gas, fine chemicals and pharmaceuticals.
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Paragraph 000115; 000116
(2018/03/09)
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- Chelating carbene ligand precursors and their use in the synthesis of metathesis catalysts
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Chelating ligand precursors for the preparation of olefin methathesis catalysts are disclosed. The resulting catalysts are air stable monomeric species capable of promoting various methathesis reactions efficiently, which can be recovered from the reaction mixture and reused. Internal olefin compounds, specifically beta-substituted styrenes, are used as ligand precursors. Compared to terminal olefin compounds such as unsubstituted styrenes, the beta-substituted styrenes are easier and less costly to prepare, and more stable since they are less prone to spontaneous polymerization. Methods of preparing chelating-carbene methathesis catalysts without the use of CuCl are disclosed. This eliminates the need for CuCl by replacing it with organic acids, mineral acids, mild oxidants or even water, resulting in high yields of Hoveyda-type methathesis catalysts. The invention provides an efficient method for preparing chelating-carbene metathesis catalysts by reacting a suitable ruthenium complex in high concentrations of the ligand precursors followed by crystallization from an organic solvent.
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Page/Page column 11
(2016/12/22)
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- Ruthenium and Osmium Heterocyclic Carbene Metathesis Catalysts
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The present invention refers to novel ruthenium- and osmium-based catalysts for olefin metathesis reactions with high Z-selectivity. The effect is obtained by utilising two monoanionic ligands (X) and (L1) of very different steric requirement. The catalysts selectively provide the Z-isomer even in presence of air or of acids. Claimed are formulae (A) and (B); The anionic ligand "X" is defined as -CN, -N3, -NCO, -CNO, -NCS, and -NCSe. Specific embodiments for these catalysts are:
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Paragraph 0086; 0087
(2015/02/02)
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- Theory-assisted development of a robust and Z-selective olefin metathesis catalyst
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DFT calculations have predicted a new, highly Z-selective ruthenium-based olefin metathesis catalyst that is considerably more robust than the recently reported (SIMes)(Cl)(RS)RuCH(o-OiPrC6H4) (3a, SIMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene, R = 2,4,6-triphenylbenzene) [J. Am. Chem. Soc., 2013, 135, 3331]. Replacing the chloride of 3a by an isocyanate ligand to give 5a was predicted to increase the stability of the complex considerably, at the same time moderately improving the Z-selectivity. Compound 5a is easily prepared in a two-step synthesis starting from the Hoveyda-Grubbs second-generation catalyst 3. In agreement with the calculations, the isocyanate-substituted 5a appears to be somewhat more Z-selective than the chloride analogue 3a. More importantly, 5a can be used in air, with unpurified and non-degassed substrates and solvents, and in the presence of acids. These are traits that are unprecedented among highly Z-selective olefin metathesis catalysts and also very promising with respect to applications of the new catalyst. This journal is the Partner Organisations 2014.
- Occhipinti, Giovanni,Koudriavtsev, Vitali,Toernroos, Karl W.,Jensen, Vidar R.
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supporting information
p. 11106 - 11117
(2014/07/21)
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- Testing the 1,1,3,3-tetramethyldisiloxane linker in olefin metathesis
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Compounds 12-15, possessing two styrenes connected by a silicon linker [1,1,3,3 tetramethyl-di-siloxane], were synthesized, characterized and used as model compounds for the ring-closing metathesis (RCM) catalyzed by commercially available ruthenium catalysts 1, 2 and 3. The RCM reactions of 12 and 15 in the presence of catalysts 1 or 2 resulted exclusively in the formation of (E)-stilbenes. The RCM reactions of 13 and 14, compounds possessing alkoxide substituents in the ortho position to styrene functionality, were not observed in the presence of 2, presumably due to the formation of inactive Hoveyda type ruthenium complexes. The RCM of mixture of 12 and 15, with 2, was used for the detailed examination of the mechanism of metathesis reactions investigated in this work. They revealed that both inter- and intramolecular metathesis is possible, in this case, despite the use of siloxane linker.
- Jab?onka-Gronowska, Ewa,Witkowski, Bart?omiej,Horeglad, Pawe?,Gierczak, Tomasz,Grela, Karol
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p. 566 - 572
(2013/07/26)
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- Photogeneration of a phosphonium alkylidene olefin metathesis catalyst
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Treatment of ruthenium carbide (H2IMes)(Cl)2(PCy 3)RuC (1) with the photoacid generator (PAG) [Ph3S][OTf] (3) under 254 nm light results in a highly efficient catalyst for ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions. The reactions proceed via formation of the ruthenium phosphonium alkylidene complex [(H2IMes)(Cl)2Ru=C(H)PCy3][OTf] as the active catalytic species. In the case of ROMP of cycloalkenes, reactions do not require addition of PAG and protonation of 1 proceeds via allylic C-H bond activation of the substrate under UV light.
- Khalimon, Andrey Y.,Leitao, Erin M.,Piers, Warren E.
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p. 5634 - 5637,4
(2020/08/31)
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- METHOD FOR PREPARATION OF RUTHENIUM-BASED METATHESIS CATALYSTS WITH CHELATING ALKYLIDENE LIGANDS
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The invention relates to a method for preparation of ruthenium-based carbene catalysts with a chelating alkylidene ligand (“Hoveyda-type catalysts”) by reacting a penta-coordinated ruthenium (II)-alkylidene complex of the type (L) (Py)X1X2Ru(alkylidene) with a suitable olefin derivative in a cross metathesis reaction. The method delivers high yields and is conducted preferably in aromatic hydrocarbon solvents. The use of phosphine-containing Ru carbene complexes as starting materials can be avoided. Catalyst products with high purity, particularly with low Cu content, can be obtained.
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- Protonolysis of a ruthenium-carbene bond and applications in olefin metathesis
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The synthesis of a ruthenium complex containing an N-heterocylic carbene (NHC) and a mesoionic carbene (MIC) is described wherein addition of a Br?nsted acid results in protonolysis of the Ru-MIC bond to generate an extremely active metathesis catalyst. Mechanistic studies implicated a rate-determining protonation step in the generation of the metathesis-active species. The activity of the NHC/MIC catalyst was found to exceed those of current commercial ruthenium catalysts.
- Keitz, Benjamin K.,Bouffard, Jean,Bertrand, Guy,Grubbs, Robert H.
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p. 8498 - 8501
(2011/07/30)
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- Switched stereocontrol in Grubbs - Hoveyda complex catalyzed ROMP utilizing proton-switched NHC ligands
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Grubbs-Hoveyda and Grubbs III type complexes with ferrocenyl- or -NEt 2-substituted NHC ligands were synthesized according to standard procedures. The electron donation of the NHC ligands in the respective ruthenium complexes can be modulated by oxidation of the ferrocenyl moiety or by protonation of the amino group. The neutral and the respective cationic (oxidized or protonated) ruthenium complexes were tested in the ROMP of norbornene. The change in the electron donation of the NHC ligands upon protonation leads to a significant change in the double-bond geometry (from E/Z ratio = 0.78 to E/Z = 1.04) and in the microstructure of the resulting polynorbornene. Consequently, addition of acid and protonation of the living catalyst attached to the polymer chain during the polymerization reaction allows fine-tuning the E/Z ratio of the resulting polynorbornene.
- Peeck, Lars H.,Leuthaeusser, Steffen,Plenio, Herbert
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p. 4339 - 4345
(2011/01/03)
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- Kinetic and thermodynamic analysis of processes relevant to initiation of olefin metathesis by ruthenium phosphonium alkylidene catalysts
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Initiation processes in a family of ruthenium phosphonium alkylidene catalysts, some of which are commercially available, are presented. Seven 16-electron zwitterionic catalyst precursors of general formula (H 2lMes)(Cl)3Ru=C(H)P(Rs
- Leitao, Erin M.,Van Der Eide, Edwin F.,Romero, Patricio E.,Piers, Warren E.,McDonald, Robert
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p. 2784 - 2794
(2010/06/11)
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- PREPARATION OF CATALYSTS
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The present invention discloses a novel synthesis method for a catalyst of formula (6), wherein n is an integer from 1 to 3, R1 is a substituent and L is a neutral ligand.
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Page/Page column 14-15
(2008/06/13)
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- Regarding the mechanism of olefin metathesis with sol-gel-supported Ru-based complexes bearing a bidentate carbene ligand. Spectroscopic evidence for return of the propagating Ru carbene
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Two isotopically and structurally labeled Ru-based carbenes (2-d 4 and 13) have been prepared and attached to the surface of monolithic sol-gel glass. The resulting glass-supported complexes (18-d n and 19) exhibit significant catalytic activity in promoting olefin metathesis reactions and provide products of high purity. Through analysis of the derivatized glass pellets used in a sequence of catalytic ring-closing metathesis reactions mediated by various supported Ru carbenes, it is demonstrated that free Ru carbene intermediates in solution can be scavenged by support-bound styrene ether ligands prior to the onset of competing transition metal decomposition. The observations detailed herein provide rigorous evidence that the initially proposed release/return mechanism is, at least partially, operative. The present investigations shed light on a critical aspect of the mechanism of an important class of Ru-based metathesis complexes (those bearing a bidentate styrene ether ligand).
- Kingsbury, Jason S.,Hoveyda, Amir H.
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p. 4510 - 4517
(2007/10/03)
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- π-face donor properties of N-heterocyclic carbenes
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The donor properties of aryl substituted N-heterocyclic carbenes are characterized by lone pair donation from the carbene carbon and, as is shown here, by donation of electron density of the aromatic π-face of the NHC aryl groups towards the metal. The Royal Society of Chemistry 2005.
- Suessner, Marcus,Plenio, Herbert
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p. 5417 - 5419
(2007/10/03)
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- Rapidly initiating ruthenium olefin-metathesis catalysts
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Vacancies: Protonation of the ruthenium carbide compounds [Cl 2(L)(PR3)Ru≡C:] gives the 14-electron four-coordinate ruthenium phosphonium alkylidenes [Cl2(L)Ru= CH(PR3)]+[B(X)4]- (see scheme). These compounds which already have a vacant coordination site provide direct access to the active species in olefin metathesis catalysis and thus very fast initiation.
- Romero, Patricio E.,Piers, Warren E.,McDonald, Robert
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p. 6161 - 6165
(2007/10/03)
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- Efficient and recyclable monomeric and dendritic Ru-based metathesis catalysts
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Several highly active, recoverable and recyclable Ru-based metathesis catalysts are presented. The crystal structure of Ru complex 5, beating a 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene and styrenyl ether ligand is disclosed. The heterocyclic ligand significantly enhances the catalytic activity, and the styrenyl ether allows for the easy recovery of the Ru complex. Catalyst 5 promotes ring-closing metathesis (RCM) and the efficient formation of various trisubstituted olefins at ambient temperature in high yield within 2 h; the catalyst is obtained in >95% yield after silica gel chromatography and can be used directly in subsequent reactions. Tetrasubstituted olefins can also be synthesized by RCM reactions catalyzed by 5. In addition, the synthesis and catalytic activities of two dendritic and recyclable Ru-based complexes are disclosed (32 and 33). Examples involving catalytic ring-closing, ring-opening, and cross metatheses are presented where, unlike monomer 5, dendritic 33 can be readily recovered.
- Garber, Steven B.,Kingsbury, Jason S.,Gray, Brian L.,Hoveyda, Amir H.
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p. 8168 - 8179
(2007/10/03)
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