Mikrostruktur von Polynorbornen

Karafilidis, Christos; Angermund, Klaus; Gabor, Barbara; Rufińska, Anna; Mynott, Richard; Breitenbruch, Georg; Thiel, Walter; Fink, Gerhard

doi:10.1002/ange.200604264

Cited by 6 publications

(7 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Moreover, a complex stereochemistry and even connectivity in the polymers obtained by vinylic polymerization of norbornene has been reported. [28][29][30] In other words, the polymers cannot be expected to possess a regular structure. Accordingly, the 119 Sn{ 1 H} spectra display one broad signal with a characteristic trialkyltin chloride chemical shift value (d = 144 ppm).…”

Section: Resultsmentioning

confidence: 97%

Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction

Carrera¹,

Gutiérrez²,

Benavente³

et al. 2008

Chemistry A European J

View full text Add to dashboard Cite

New functionalized polynorbornenes have been obtained in good yields by vinylic copolymerization of norbornene with a (norbornenyl)SnBu(2)Cl monomer, catalyzed by [Ni(C(6)F(5))(2)(SbPh(3))(2)]. Subsequent functionalization produces a wide variety of polymers with different --SnBu(2)R groups (R=aryl, vinyl, alkynyl). The polymers can be used as R-transfer reagents in Stille couplings, thereby providing easy workup and separation of the polymeric tin byproducts from the coupling products. Tin contents of around 0.05 wt % are found in the Stille products. The stannylated polymers can be recycled and reused with good efficiency.

show abstract

Section: Resultsmentioning

confidence: 97%

Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction

Carrera¹,

Gutiérrez²,

Benavente³

et al. 2008

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…No signals attributable to a 1,7‐connectivity of poly(NBE) VIP sequences were observed 90. 91 The most important signals, however, were found at δ =132.99, 132.94, 132.88, and 132.71 and at δ =42.91, 41.84, 32.98, and 32.41 ppm (Figure S9 in the Supporting Information). These signals are absent in the spectrum of pure poly(NBE) ROMP as well as in that of poly(NBE) VIP ‐ co ‐poly(E)57 and can be unambiguously assigned to poly(NBE) ROMP ‐ alt ‐poly(NBE) VIP sequences;57 this confirms the incorporation of poly(NBE) ROMP units into the polymer main chain by reversible α‐H elimination/addition.…”

Section: Resultsmentioning

confidence: 99%

“…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

View full text Add to dashboard Cite

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.

show abstract

“…No signals indicative of a 1,7connectivity 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.…”

mentioning

confidence: 87%

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

et al. 2011

View full text Add to dashboard Cite

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).

show abstract

Mikrostruktur von Polynorbornen

Cited by 6 publications

References 4 publications

Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction

Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction

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

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

Contact Info

Product

Resources

About