Ring-opening Metathesis Polymerization Of Norbornene Research Articles

Block Copolymers by Transformation of Living Ring-Opening Metathesis Polymerization into Controlled/“Living” Atom Transfer Radical Polymerization

A general method of transformation of living ring-opening metathesis polymerization (ROMP) into controlled/“living” atom transfer radical polymerization (ATRP) is reported for the preparation of block copolymers. For example, the macroinitiators PNB−C6H4−CH2Br (Mn = 30 520, Mw/Mn = 1.09) or PDCPD−C6H4−CH2Br (Mn = 12 100, Mw/Mn = 1.24) were prepared by ROMP of norbornene (NB) or dicyclopentadiene (DCPD) and subsequent Wittig-like reactions with p-(bromomethyl)benzaldehyde. These compounds were used as efficient macroinitiators for homogeneous controlled/“living” ATRP to prepare block copolymers with styrene (St), PNB-b-PSt (Mn = 110 400, Mw/Mn = 1.06) and PDCPD-b-PSt (Mn = 20 100, Mw/Mn = 1.37), and methyl acrylate (MA), PNB-b-PMA (Mn = 85 100, Mw/Mn = 1.07) and PDCPD-b-PMA (Mn = 25 300, Mw/Mn = 1.47).

Cis-iso-Specific Polymerization of Norbornenes by a Unique Combination of Cp* and 1,3-Butadiene Ligands on Tantalum: Crystal Structures of Cp*(η4-C4H6)Ta(CH2Ph)2 and Cp*(η4-C4H6)Ta(CHPh)(PMe3)

cis-iso-Specific homogeneous ring-opening metathesis polymerization of norbornenes is achieved by using the catalyst precursor Cp*(η4-C4H6)Ta(CH2Ph)2 (2). Thermolysis of 2 generates a benzylidene species, which is trapped by PMe3 to give a benzylidene complex Cp*(η4-C4H6)Ta(CHPh)(PMe3) (4). The crystal structures of 2 and 4 are determined by X-ray analysis.

Catalytic properties of novel chiral polyoxomolybdate(VI) salts: The ring-opening metathesis polymerization (ROMP) of norbornene

Each of the chiral polyoxomolybdate(VI) salts (R 3NH) 4[Mo 8O 26(R 3N) 2] and (Na) 2(R 3NH) 2[Mo 8O 26] (R 3N = (+)-cinchonine, (+)-hydroquinidine or (−)-quinine), in the presence of the cocatalyst EtAlCl 2, catalyses the ring-opening metathesis polymerization of norbornene at room temperature. The polynorbornene produced in these reactions was found to be mostly insoluble. Inclusion of a chain transfer agent, 1-hexene, in the reactions leads to greatly improved yields of polynorbornene which is freely soluble in chloroform, and the quantity of polymer formed is highly sensitive to the amount of 1-hexene added.

Ring Opening Metathesis Polymerization of Norbornene by WCl6: Formation of WCl5 and WCl4 and Their Catalytic Activity

Reaction between WCl6 and norbornene in benzene and cyclohexane, respectively, was investigated using UV/VIS, ESR and XPS spectroscopy in order to establish the main reaction products on the tungsten side and their relation to the initiation of ring opening metathesis polymerization (ROMP) of norbornene. The tungsten compounds: WCl5, insoluble WCl4 and soluble tungsten species having four chlorine atoms bound to tungsten, [WCl4Ln] were found to be the main products. The catalytic activity of the respective compounds in ROMP of norbornene was found to decrease in the order: WCl5 > WCl6 >> WCl4 ~ [WCl4Ln]. The polynorbornenes prepared with both WCl4 and [WCl4Ln] possess higher content of cis double bonds in comparison with polymers prepared with WCl6 and WCl5 catalysts.

Single crystals of isopolyoxometallate(VI) salts as catalysts for the ring-opening polymerization of norbornene

A single crystal of each of the isopolyoxometallate(VI) salts ( nBu 4N) 2[Mo 6O 19], ( nBu 4N) 2[W 6O 19] and ( nBu 4N) 4[W 10O 32], in combination with EtAlCl 2 cocatalyst, heterogeneously catalyses the ring-opening metathesis polymerization of norbornene at room temperature. Polymer yield is found to be dependent upon the reaction solvent, and it is generally found that the inclusion of a chain transfer reagent in the reaction mixture leads to significantly improved yields of chloroformsoluble polynorbornene.

The role of two-component catalysts containing chelating bisaryloxide ligands in controlling the stereochemistry of the metathesis polymerization of norbornene

The ring-opening metathesis polymerization of norbornene and 5,5-dimethylnorbornene has been studied with a range of tungsten(VI) ring-opening metathesis polymerization procatalysts containing chelating diolate ligands, including catechols, 1,8-dihydroxynaphthalene, 1,1′-bi-2-naphthol, biphenanthrol and bis(2-hydroxyphenyl) methane. One class of these catalysts, W(X)(OArO)Cl 2(THF) (X = O or NArMe 2) was produced via alcoholysis reactions between W(X)Cl 4 and the respective diol. Polymers of norbornene produced with these catalysts showed a reasonable correlation between ring size and cis-selectivity. This effect is most likely steric in origin. Analyses of the tacticity of poly-5,5-dimethylnorbornene showed a correlation betwen high cis-olefin content and syndiotacticity, even when produced with catalysts containing asymmetric chelating diolate ligands.

Mo2(MeCN)8][BF4]4 supported on silica: an efficient heterogeneous catalyst for the ring-opening metathesis polymerization of norbornene

The dimolybdenum(II,II) complex salts [Mo2(MeCN)8][BF4]4, and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 have been supported on silica to give materials represented as [Mo2(MeCN)8][BF4]4–SiO2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2, respectively. Unsupported [Mo2(MeCN)8][BF4]4, [Mo2(MeCN)8][BF4]4–SiO2, unsupported [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2 were each tested as heterogeneous catalysts for the ring-opening metathesis polymerization of norbornene (bicyclo[2.2.1]hept-2-ene). In the absence of AlEtCl2 cocatalyst [Mo2(MeCN)8][BF4]4–SiO2was the only species to polymerize norbornene, and at 90°C and a reaction time of 48 h the polymerization was essentially quantitative. Species [Mo2(MeCN)8][BF4]4. [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2 were found to be completely inactive without AlEtCl2, even at elevated temperatures. In the presence of AlEtCl2 cocatalyst [Mo2(MeCN)8][BF4]4–SiO2 was the only material which failed to polymerize norbornene at room temperature.

Ring-opening metathesis polymerization of norbornene with titanium alkylidenes generated by thermolysis of dimethyltitanocene and related cyclopentadienyltitanium(IV) derivatives

Heating norbornene in the presence of catalytic amounts of dimethyltitanocene, cyclopentadienyltrimethyltitanium(IV), chlorodimethylcyclopentadienyltitanium(IV), and bis[(trimethylsilyl)methyl]titanocene resulted in the ring-opening metathesis polymerization of norbornene. Presumably, the in-situ generation of free or complexed titanium alkylidene intermediates is responsible for these polymerizations. The use of tetrahydrofuran as the solvent had a significant inhibitory effect that varied with the initiator used. This effect was confirmed with the measurement of kinetic data. This substituent-dependent solvent effect was attributed to changes in the relative contributions of nucleophilic and neutral resonance structures, in agreement with recent theoretical calculations

Electron-deficient vanadium alkyl complexes: synthesis and molecular structure of the vanadium(III) dinitrogen complex [(Me3CCH2)3V]2(.mu.-N2)

The vanadium(III) dinitrogen-bridged complex [(Me3CCH2)3V]2(mu-N2) (1), obtained from reaction Of VCl3(THF)3 and Me3CCH2Li under nitrogen, is converted to the vanadium(V) oxo complex OV(CH2CMe3)3 (3) by reaction with styrene oxide. Both 1 and 3 decompose at ambient temperature to give neopentane and species which are active in the ring-opening metathesis polymerization of norbornene.

Ring-opening polymerization of norbornene using a single crystal of (Bun 4N)2[Mo6O19] as a heterogeneous catalyst

A single monoclinic crystal of the isopolymolybdate(VI) salt (Bun4N)2[Mo6O19] when treated with an alkylaluminium compound is an efficient and totally recoverable heterogeneous catalyst for the ring-opening metathesis polymerization of norbornene.

Chain-end functionalization of living polymers formed by the ring-opening metathesis polymerization of norbornene

Preparation des polymeres tBu-CH(=CH-(C 5 H 8 )-CH) n =CH-PhX (X=OMe, NMe 2 , CN, NO 2 , CHO, CO 2 MC, NH 2 , CF 3 -Cl) par reaction du polymere vivant avec le benzaldehyde substitue correspondant

The mechanism of stereoselective ring-opening metathesis polymerization of norbornene and several derivatives

The properties of several noble metal halide catalysts for ring-opening metathesis polymerization of norbornene, endo-dicyclopentadiene and norbomadiene have been investigated as a function of prior or in situ treatment by the latter pair of diolefins, which may also be monomers as stated. Microstructures of the various polymers and sometimes copolymers were examined in detail using 13C NMR, 1H NMR and IR spectroscopic techniques. In the case of Ru and Os chlorides, there is a dramatic swing from high- trans to high- cis polymer in all cases where chelating diolefin is present, whereas IrCl 3 is unaffected in this respect. High- cis polymers of norbornene, made using RhCl 3 and endo-dicyclopentadiene-modified RuCl 3, show a strong tendency for the small number of trans units that are present to occur in triplets and larger blocks, an unusual blockiness feature previously noted only when the OsCl 3 catalyst was used. The usual tendency for high- cis-poly(norbornene) made using numerous Mo, W and Re based catalysts is to have the trans units in pairs. In all cases, therefore, there is a virtual absence of ctc triads, in contradiction to expectation for random high- cis polymers. This general feature is discussed in terms of a new mechanism based on two or more kinetically distinct metallacarbenes and various conformational forms of metallacyclobutanes undergoing disrotatory [2 + 2] cycloreversion reactions.