Metallocenkatalysierte C7‐Verknüpfung in der Hydrooligomerisierung von Norbornen durch σ‐Bindungs‐Metathese: Einblick in die Mikrostruktur von Polynorbornen

Karafilidis, Christos; Hermann, H; Rufińska, Anna; Gabor, Barbara; Mynott, Richard; Breitenbruch, Georg; Weidenthaler, Claudia; Rust, Jörg; Joppek, Werner; Brookhart, Maurice; Thiel, Walter; Fink, Gerhard

doi:10.1002/ange.200353454

Cited by 10 publications

(21 citation statements)

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“…No signals indicative of a 1,7-connectivity of poly(NBE) VIP sequences were observed. [35,36] These findings exclude the presence of the two polymers poly(NBE) ROMP and poly(NBE) VIP -co-poly(E) as well as the following alternative pathway: Poly(NBE) ROMP could form by initial a elimination followed by cleavage of the titanium alkylidene by E, which would result in a vinyl-terminated polymer. This macromonomer could then copolymerize with NBE and E. In fact, our data support the reaction mechanism shown in Scheme 3: Reaction of a cationic VIP-active species with NBE, followed by a elimination produces a disubstituted titanium alkylidene whose formation is favored over the formation of a monosubstituted alkylidene from the a elimination after E insertion.…”

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confidence: 87%

A Catalyst for the Simultaneous Ring‐Opening Metathesis Polymerization/Vinyl Insertion Polymerization

et al. 2011

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Dedicated to Professor Walter Kaminsky on the occasion of his 70th birthdayBoth the vinyl insertion polymerization (VIP) of olefins [1][2][3][4][5][6][7] and the ring-opening metathesis polymerization (ROMP) [8,9] of cyclic olefins are well-established polymerization techniques based on the insertion of a monomer between a transition metal (ion) and a growing polymer chain. In fact, they are related to each other, since a cationic, VIP-active catalyst may be converted into a ROMP-active catalyst by a simple a-elimination process. In contrast, the reverse process, that is, the a addition of a proton to a metal alkylidene to form a cationic VIPactive species, is much more difficult to accomplish in a controlled way.The occurrence of both VIP-(Scheme 1 a) and ROMP-derived (Scheme 1 b) structures in poly(NBE) (NBE = norborn-2-ene) was observed already in the early days of polyolefin chemistry and paved the way for identifying and understanding metathesis-based processes. [10,11] Nevertheless, at that time there was no clear evidence for the presence of both structures, that is, both ROMP-and VIP-derived repeat units, within one single polymer chain. [10][11][12][13][14] In fact, because of the high crystallinity of these polymers, it was argued that two different polymers, that is, one VIP-and one ROMP-derived, had formed concomitantly. The first unequivocal evidence for the presence of both ROMP-and VIP-derived structures within one single polymer chain was reported by Farina et al. using Mo-and Re-based initiators; [15,16] they unambiguously assigned characteristic signals for the quaternary carbon and for the methylene group in VIP/ROMP-derived poly(NBE) (Scheme 1 c).In fact, the structure of this particular polymer can be explained only by a reversible a-elimination/a-addition process, which permits VIP and ROMP to take place within the same polymer chain. Owing to the relationship between VIP and ROMP, even one single switch between VIP and ROMP, resulting in the synthesis of AB diblock copolymers, has attracted attention. Thus, Grubbs et al. reported on a titanacyclobutane compound active in the ROMP of NBE; upon addition of an alcohol and activation with Et 2 AlCl, a cationic species was created that is active in the VIP of ethylene (E), resulting in the synthesis of poly(NBE) ROMP -bpoly(E).[17] Kaminsky et al. reported on a controlled switch from VIP to ROMP in the preparation of poly(NBE) VIP -bpoly(NBE) ROMP , poly(NBE) VIP -b-poly(CPE) ROMP , and poly-(NBE) VIP -b-poly(COE) ROMP (CPE = cyclopentene, COE = cis-cyclooctene).

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A Catalyst for the Simultaneous Ring‐Opening Metathesis Polymerization/Vinyl Insertion Polymerization

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“…In no case were any signals attributable to a 1,7-connectivity of polyA C H T U N G T R E N N U N G (NBE) VIP sequences observed. [90,91] None of the copolymers showed signals for ROMP-derived polyA C H T U N G T R E N N U N G (NBE) ROMP . As expected, an increase in polymerization temperature resulted in a decrease in M n .…”

Section: Copolymerization Of Ethylene (E) With Norborn-2-ene (Nbe)mentioning

confidence: 99%

Group 4 Dimethylsilylenebisamido Complexes Bearing the 6‐[2‐(Diethylboryl)phenyl]pyrid‐2‐yl Motif: Synthesis and Use in Tandem Ring‐Opening Metathesis/Vinyl‐Insertion Copolymerization of Cyclic Olefins with Ethylene

Zou

Wang

Wurst

et al. 2011

Chemistry A European J

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Two novel Zr(IV)- and Hf(IV)-based bisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif, that is, [ZrCl(2){Me(2)Si(DbppN)(2)}(thf)] (9) and [HfCl(2){Me(2)Si(DbppN)(2)}(thf)(2)] (10) (DbppN=6-[2-(diethylboryl)phenyl]pyridine-2-amido) have been prepared. Their reactivities have been compared with that of a model precatalyst that does not bear the aminoborane motif. Upon activation with methylalumoxane, precatalysts 9 and 10 are active in the homopolymerization of ethylene (E) yielding high-density polyethylene (HDPE). In the copolymerization of E with cyclopentene (CPE), for example by the action of 9, the presence of CPE resulted in a dramatic increase in the polymerization activity of E, while CPE incorporation remained close to or at zero. In the vinyl-insertion copolymerization of norborn-2-ene (NBE) with E by the action of 9, statistical cyclic olefin copolymers of these two monomers were obtained. At higher NBE concentrations, however, 9 gave rise to reversible ring-opening metathesis (ROMP)/vinyl-insertion polymerization (VIP) of NBE with E, resulting in the formation of multi-block copolymers of the general formula poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E). This particular feature of precatalyst 9, that is, the ability to induce a reversible α-H elimination/α-H addition reaction, is attributed to the unique role of the 6-[2-(diethylboryl)phenyl]pyrid-2-yl ligand. Accordingly, a model precatalyst lacking this ligand does not have the ability to induce α-H elimination/α-H addition reactions. The different (11)B NMR shifts of various diethylborylphenylpyrid-2-ylamines and -amides permit a ranking of the strengths of the B-N bonds in these compounds. This strength of the B-N bond is correlated with the propensity of 9/MAO to produce poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E) at different temperatures.

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“…Zusätzlich sind E-NBE-E-E-Sequenzen zu beobachten. Die Signale bei d = 46.8 und 41.1 ppm entsprechen den alternierenden, syndiotaktischen, VIP-abgeleiteten E-NBE-Sequenzen, [29][30][31][32][33][34] [35,36] Dies schließt die Gegenwart zweier unabhängiger Polymere, d. h. von Poly(NBE) ROMP und Poly(NBE)VIP-co-poly(E), sowie einen alternativen Reaktionsweg über die Bildung von Poly(NBE) ROMP via a-Eliminierung und Spaltung des gebildeten Titanalkyliden-Intermediats durch E unter Bildung eines vinylterminierten Polymers aus. Dieses Makromonomer könnte dann mit NBE und E copolymerisieren.…”

Section: Professor Walter Kaminsky Zum 70 Geburtstag Gewidmetunclassified

Ein Katalysator für die Tandem‐Ringöffnungsmetathesepolymerisation/Vinylinsertionspolymerisation

et al. 2011

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Metallocenkatalysierte C7‐Verknüpfung in der Hydrooligomerisierung von Norbornen durch σ‐Bindungs‐Metathese: Einblick in die Mikrostruktur von Polynorbornen

Cited by 10 publications

References 11 publications

A Catalyst for the Simultaneous Ring‐Opening Metathesis Polymerization/Vinyl Insertion Polymerization

A Catalyst for the Simultaneous Ring‐Opening Metathesis Polymerization/Vinyl Insertion Polymerization

Group 4 Dimethylsilylenebisamido Complexes Bearing the 6‐[2‐(Diethylboryl)phenyl]pyrid‐2‐yl Motif: Synthesis and Use in Tandem Ring‐Opening Metathesis/Vinyl‐Insertion Copolymerization of Cyclic Olefins with Ethylene

Ein Katalysator für die Tandem‐Ringöffnungsmetathesepolymerisation/Vinylinsertionspolymerisation

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