Showing papers on "Norbornene published in 2004"
TL;DR: The reaction mechanism of olefin metathesis by ruthenium carbene catalysts is studied by gradient-corrected density functional calculations (BP86) and the most likely dissociative mechanism with trans Olefin coordination is investigated.
Abstract: The reaction mechanism of olefin metathesis by ruthenium carbene catalysts is studied by gradient-corrected density functional calculations (BP86). Alternative reaction mechanisms for the reaction of the “first-generation” Grubbs-type catalyst (PCy3)2Cl2RuCH2 (1) for the reaction with ethylene are studied. The most likely dissociative mechanism with trans olefin coordination is investigated for the metathesis reaction between the “first-” and the “second-generation” Grubbs-type catalysts 1 and (H2IMes)(PCy3)Cl2RuCH2 (2) with different substrates, ethylene, ethyl vinyl ether, and norbornene, and a profound influence of the substrate is found. In contrast to the degenerate reaction with ethylene, the reactions with ethyl vinyl ether and norbornene are strongly exergonic by 8−15 kcal/mol, and this excess energy is released after passing through the metallacyclobutane structure. While the metallacyclobutane is in a deep potential minimum for degenerate metathesis reactions, the energy barrier for the [2+2] cy...
261 citations
TL;DR: Transmission electron microscopy indicated that the PE-b-poly(ethylene-co-norbornene) possesses high potential as a new material consisting of crystalline and amorphous segments which are chemically linked.
Abstract: Bis(pyrrolide−imine) Ti complexes in conjunction with methylalumoxane (MAO) were found to work as efficient catalysts for the copolymerization of ethylene and norbornene to afford unique copolymers via an addition-type polymerization mechanism. The catalysts exhibited very high norbornene incorporation, superior to that obtained with Me2Si(Me4Cp)(N-tert-Bu)TiCl2 (CGC). The sterically open and highly electrophilic nature of the catalysts is probably responsible for the excellent norbornene incorporation. The catalysts displayed a marked tendency to produce alternating copolymers, which have stereoirregular structures despite the C2 symmetric nature of the catalysts. The norbornene/ethylene molar ratio in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. At norbornene/ethylene ratios larger than ca. 1, the catalysts mediated room-temperature living copolymerization of ethylene and norbornene to form high molecular weight monodisperse copolyme...
192 citations
TL;DR: Biphenylylalkenes containing an ortho substituent in one ring and a different ortho-, meta-, or para-substituent in the other are prepared in satisfactory yield from an orthosubstituted aryl iodide, a terminal olefin, and a base in DMF under the joint catalytic action of palladium(0) and norbornene.
Abstract: Biphenylylalkenes containing an ortho substituent in one ring and a different ortho-, meta-, or para-substituent in the other are prepared in satisfactory yield from an ortho-substituted aryl iodide, an ortho-, meta-, or para-substituted aryl bromide, a terminal olefin, and a base in DMF under the joint catalytic action of palladium(0) and norbornene.
185 citations
TL;DR: The 4a-d/MMAO catalyst system is also capable of promoting the quasi-living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight alternating copolymers with narrow molecular weight distributions.
168 citations
TL;DR: In this article, the authors describe two methods to synthesize bottlebrush polymers with molecular weights from 1 million to over 60 million g mol-1 using Grubbs' first and second generation catalysts.
Abstract: This paper describes two methods to synthesize bottlebrush polymers with molecular weights from 1 million to over 60 million g mol-1 using Grubbs' first and second generation catalysts. In the first method, macromonomers of poly(l-lactide) were synthesized using tin(II) 2-ethylhexanoate and terminated on one end with a norbornyl group. Grubbs' first generation catalyst polymerized macromonomers with one poly(l-lactide) chain per norbornene, and Grubbs' second generation catalyst polymerized macromonomers with two poly(l-lactide) chains per norbornene. The predicted and measured molecular weights closely matched each other, and the polydispersities of the bottlebrush polymers were between 1.05 and 1.39. These examples are the first where Grubbs' second generation catalyst can be considered living for ROMP. In the second method, the backbone was polymerized first, and polylactide arms with molecular weights from 15 000 to 50 000 g mol-1 were polymerized from the backbone. Polymers that were shaped as sphere...
166 citations
TL;DR: In this article, Picolyl-functionalized N-heterocyclic carbene complexes have been synthesized by a route involving carbene transfer from Ag(I) carbene precursors.
157 citations
TL;DR: Vinylideneruthenium complexes with the general formula [RuCl2(=C=CHR)L2] (L = PPr3i, PCy3, etc.) have been found to serve as good catalyst precursors with high efficiencies for ring-opening metathesis polymerization of cyclic olefins, ring opening/cross-metathesis between norbornene derivatives and vinyl chalcogenides, and (Z)-selective dimerization of terminal alkynes as mentioned in this paper.
139 citations
TL;DR: The use of surface-initiated ring-opening metathesis polymerization (SI- ROMP) for producing polymer dielectric layers is reported, demonstrating for the first time that SI-ROMP can be used in the construction of organic thin-film electronic devices.
Abstract: The use of surface-initiated ring-opening metathesis polymerization (SI-ROMP) for producing polymer dielectric layers is reported. Surface tethering of the catalyst to Au or Si/SiO2 surfaces is accomplished via self-assembled monolayers of thiols or silanes containing reactive olefins. Subsequent SI-ROMP of norbornene can be conducted under mild conditions. Pentacene semiconducting layers and gold drain/source electrodes are deposited over these polymer dielectric films. The resulting field effect transistors display promising device characteristics, demonstrating for the first time that SI-ROMP can be used in the construction of organic thin-film electronic devices.
130 citations
TL;DR: A series of neutral nickel complexes with Schiff-base ligands was synthesized and characterized by X-ray single-crystal analyses in this article, which showed high catalytic activities of up to 3.16 x 10(7) g PNB mol(-1) Ni h(-1), for the addition polymerization of norbornene in the presence of modified methylaluminoxane (MMAO) as cocatalyst.
124 citations
TL;DR: In this paper, Ethene−norbornene (E−N) copolymerizations were carried out by (t-BuNSiMe2Flu)TiMe2 (1) with methylaluminoxane (free from Me3Al) under an atmospheric pressure of ethene at 40 °C 1 showed higher activity than 2 The activity of 1 increased with increasing the feed ratio of norbornene/ethene, but the opposite trend was observed for 2 in the same feed ratio (N/E = 8), while the incorporation of nor
Abstract: Ethene−norbornene (E−N) copolymerizations were carried out by (t-BuNSiMe2Flu)TiMe2 (1) and (t-BuNSiMe2C5Me4)TiMe2 (2) activated with methylaluminoxane (free from Me3Al) under an atmospheric pressure of ethene at 40 °C 1 showed higher activity than 2 The activity of 1 increased with increasing the feed ratio of norbornene/ethene, but the opposite trend was observed for 2 In the same feed ratio (N/E = 8), the incorporation of norbornene was higher with 1 (N = 50 mol %) than with 2 (N = 38 mol %) The 13C NMR spectrum of the E−N copolymer obtained with 1 was completely different from that with 2 The former showed the resonances of norbornene dyad and triad, whereas the latter showed only those of alternating and isolated norbornene structures Some new signals were assigned to the rac,rac-NNN triad The effects of activators and polymerization temperature were investigated with 1 in more detail, and the 1-Ph3CB(C6F5)4/Oct3Al system was found to show the highest activity at 80 °C and gave the E−N copolyme
110 citations
TL;DR: Several tantalum imido complexes have been synthesized and shown to efficiently catalyze the hydroamination of internal and terminal alkynes, and factors affecting catalyst activity and selectivity are discussed.
TL;DR: A series of novel nickel complexes bearing anilido−imine ligands, (Ar1NCHC6H4NAr2)NiBr]2, have been synthesized and characterized as mentioned in this paper.
TL;DR: The effect of substituent on the palladium(II)-catalyzed addition polymerization of functionalized norbornene derivatives was examined in this article, where it was shown that endo-substituted norbornenes are polymerized more slowly than their corresponding exo isomers.
TL;DR: In this paper, the polymerization behavior of novel polynuclear cage complexes as precatalysts in the vinyl or addition polymerization of norbornene has been investigated and correlated with the results of the known mononuclear precataliasts M(acac) x (M=Ni II, Co III, Cr III, and Fe III, acac=acetylacetonate, x =2 or 3) and mixtures thereof.
TL;DR: In this article, single-walled carbon nanotubes were oxidatively shortened and functionalized with ruthenium-based olefin metathesis catalysts, resulting in rapid polymerization from the catalyst sites on the nanotube.
Abstract: Single-walled carbon nanotubes were oxidatively shortened and functionalized with ruthenium-based olefin metathesis catalysts. These catalyst-functionalized nanotubes were shown to be effective in the ring-opening metathesis polymerization of norbornene, resulting in rapid polymerization from the catalyst sites on the nanotube. It was found that high polymer molecular weights could be reached, and the molecular weight increased linearly with polymerization time. The resulting polynorbornene-functionalized nanotubes were found to exhibit solubility in organic solvents, whereas the starting materials and catalyst-functionalized nanotubes were completely insoluble. The polymerized materials were characterized by NMR, IR, DSC, AFM, and TEM.
TL;DR: Vinyl-addition poly(norbornene) copolymers functionalized with nonlinear optical chromophore side groups have been prepared using (η6-toluene)Ni(C6F5)2, and their electrooptic properties have been characterized.
Abstract: Vinyl-addition poly(norbornene) copolymers functionalized with nonlinear optical chromophore side groups have been prepared using (η6-toluene)Ni(C6F5)2, and their electrooptic properties have been characterized. The nickel complex used to polymerize the norbornene monomers is tolerant to many functional groups found in nonlinear optical chromophores although nitriles and amines other than trisubstituted amines strongly inhibit the reaction. A vinyl-addition copolymer of hexylnorbornene and a norbornene-functionalized Disperse Red 1 chromophore was scaled up and studied in detail. Initial studies indicate that electric field poling is effective but that relaxation of polar order in the poly(norbornene) is faster than in a comparable methacrylate copolymer.
TL;DR: An intermolecular hydroamination reaction of norbornene is presented that uses catalytic amounts of user-friendly TiCl(4) and tolerates a variety of functional groups and a secondary amine is converted using this methodology.
TL;DR: A series of neutral palladium(II) complexes bearing non-symmetric bidentate pyrrole-iminato or salicylaldiminiato chelate ligands have been synthesized, and the structure of representative complexes (3a, 4a, and 5a) have been confirmed by X-ray crystallographic analysis as mentioned in this paper.
TL;DR: In this article, a model study with four norbornene derivatives with different groups connecting a functional unit to the norbornenes reveals that the anchor groups influence the polymerization rate constants of ring opening metathesis (ROM) polymerisations.
Abstract: A model study with four norbornene derivatives with different groups connecting a functional unit to the norbornene reveals that the anchor groups influence the polymerisation rate constants of ring opening metathesis (ROM) polymerisations. Consequently, polydispersities and molecular weights are affected. The observed effects are explained by different tendencies of the anchort groups to coordinate to the ruthenium centre during the resting state of the propagation. A funectionalised monomer where F is the functional unit, S is a spacer, A is an anchor group and P is the polymerisable group.
TL;DR: In this paper, a ring-opening metathesis polymerization (ROMP) was used to synthesize gradient copolymers of exo-5-(benzyloxy)norbornene and exo −5-[(4-tert-butyl) benzyloxyl] norbornene.
Abstract: Gradient copolymers of exo-5-(benzyloxy)norbornene and exo-5-[(4-tert-butyl)benzyloxy]norbornene were synthesized via ring-opening metathesis polymerization (ROMP). Kinetic studies revealed that the reactivity ratios of both monomers were close to unity. As predicted, this monomer pair did not result in copolymers with significant gradients under batch polymerization conditions. However, semibatch conditions resulted in copolymers with sizable gradients whose shape was independent of the rate of addition. Addition of the monomers simultaneously via a dual and opposite ramping strategy led to a 50/50 copolymer with an exceptionally linear gradient. These gradient copolymers were further functionalized via hydrogenation, bromination, and bromoalkoxylation.
TL;DR: In this paper, a ring-opening metathesis polymerization of this type of modular monomer was studied using a molybdenum alkylidene catalyst (7) and three different ruthenium carbene catalysts (8−10).
Abstract: Novel 2,3-disubstituted-7-alkylidene norborn-2-ene derivatives (1−4) were prepared through Diels−Alder cycloaddition of fulvene derivatives and appropriate dienophiles. The ring-opening metathesis polymerization of this type of modular monomer was studied using a molybdenum alkylidene catalyst (7) and three different ruthenium carbene catalysts (8−10). Through the choice of monomer and catalyst it was possible to obtain polymers with a range of molecular weights and narrow polydispersities (1.08−1.20). The resulting polymers were quantitatively transformed to water-soluble amphiphilic polymers through simple chemical modifications. By changing the monomer structure, it was possible to tune the balance of hydrophobicity and ionic nature of the final polymer. The interaction of these polymers with phospholipid membranes was studied using large unilamellar vesicles that entrap a fluorescent dye. To probe the effect of polymer molecular weight, ionic nature, and hydrophobic character on membrane disruption ac...
TL;DR: The results of these studies suggest that the bond between the sulfoximine nitrogen atom and the carbonyl group has a less pronounced double-bond character than the corresponding bond in an amide, supported by the first X-ray crystal structure of a sulfoxIMidoyl derivative.
Abstract: N-Acylated sulfoximines display unique chemical properties. Various derivatives have been synthesized and investigated by NMR and IR spectroscopy. The results of these studies suggest that the bond between the sulfoximine nitrogen atom and the carbonyl group has a less pronounced double-bond character than the corresponding bond in an amide. This assumption is supported by the first X-ray crystal structure of a sulfoximidoyl derivative. Ab initio calculations (MP2/6-311++G**) provide further insight into the electronic nature of the N-acyl fragment. Studies of the chemical behavior of N-acylated sulfoximines indicate the presence of a highly electrophilic carbonyl group. Thus, the N--C(O) bond can easily be cleaved under mild basic conditions, and the acidity of the hydrogen atoms alpha to the sulfoximine carbonyl group is high. As a consequence of the latter property, endo,endo-sulfoximidoyl norbornene derivatives readily isomerize to their endo,exo counterparts, and sulfoximine-containing pseudopeptides can easily epimerize at the stereogenic center next to the N--C(O) carbonyl group.
TL;DR: In this article, a poly(norbornene) has been functionalized with aluminum tris(8-hydroxyquinoline) (Alq3), the emission and electron-transport layer of choice in organic light-emitting diodes.
Abstract: Poly(norbornene) has been functionalized with aluminum tris(8-hydroxyquinoline) (Alq3), the emission and electron-transport layer of choice in organic light-emitting diodes. The resulting polymer c...
TL;DR: A series of nickel(II) complexes bearing two nonsymmetric bidentate beta-ketoiminato chelate ligands have been prepared, and the structures of complexes were confirmed by X-ray crystallographic analysis as mentioned in this paper.
TL;DR: In this paper, the picolyl-functionalized o-carborane ligand CabNH (1; CabNH = 1-(2‘-picolyl)-o-Carborane) was prepared from the monolithium carborane LiHC2B10H10 (=LiCab) and 2-CH2ClC5H5N.
TL;DR: In this article, the authors described a method for polymerization viavinyl addition with (t-BuNSiMe2Flu)TiMe2 (1) in the presence of various cocatalysts [methylaluminoxane (MAO), modified methyl aluminoxANE (MMAO) and Ph3CB(CB)
Abstract: Norbornene polymerization via “vinyl addition” proceeded with (t-BuNSiMe2Flu)TiMe2 (1) in the presence of various cocatalysts [methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and Ph3CB(...
TL;DR: In this article, a high selectivity towards dialkylsubstituted diarylacetylenes and diarylalkylidenehexahydromethanofluorenes, respectively, has been reached.
TL;DR: This study rationalizes for the first time the experimentally observed reactivity differences of cyclohexene, cyclopentene, and norbornene.
Abstract: The reactivity of different Co2(CO)6−acetylene complexes in the Pauson−Khand reaction is strongly dependent on the nature of the olefin. Theoretical calculations at both the DFT and ONIOM levels are concordant with experimental observations and suggest how the olefin−cobalt interactions in the complex could have a major effect on the relative reactivity of the olefins. This study rationalizes for the first time the experimentally observed reactivity differences of cyclohexene, cyclopentene, and norbornene.
TL;DR: Complex OsHCl(CO)(P i Pr 3 ) 2 catalyzes the ring-opening metathesis polymerization (ROMP) of norbornene and 2,5-norbornadiene to give poly(norbornene) and poly(nakedadiene), respectively In both cases the resulting polymers have a high cis (74-95%) content as discussed by the authors.