Ring-opening Metathesis Polymerization Of Norbornene Research Articles

Studies on Ring-Opening Metathesis Polymerization of Norborene Catalyzed by Hydride Containing Mononuclear Ruthenium Complex

Ring-opening metathesis polymerization (ROMP) has emerged as an important tool for the preparation of architecturally unique macromolecules from cyclic olefins. A wide variety of catalytic systems, ranging from simple metal salts to highly sophisticated alkylidene metal complexes, have been used for the achievement of this synthetically useful transformation. Especially, tremendous efforts have been directed toward the ruthenium-based catalytic systems as well as the understanding of their reactivity patterns. And Grubbs catalysts represent the ultimate in terms of activity, but they are not cost effective due to the sophisticated ligand. Therefore, alternative catalyst precursors that are more readily accessible have been and are still being actively developed. Therefore, a hydride ligand containing mononuclear ruthenium complex Ru(p-cymene)HClPCy3 reported here was designed to catalyze ring-opening metathesis polymerization of norbornene with high activity. The hydride ligand is critical based on its high trans effect (for ligand dissociation) and the ability to generate carbene species through plausible migratory insertion and α-elimination steps. This catalytic system bearing hydride ligand could be an alternative for the well-defined Ru-based initiators which rules out the need of installation of complex ancillary ligands like NHC or O-Ligand in the coordination sphere or the need of activation with diazo compounds in the search for novel active catalytic species. Further study on the catalytic polymerization activity of Ru(p-cymene)H2PCy3 compared to the Ru(p-cymene)HClPCy3 system revealed that chloride ligand was also crucial to the hydride containing mononuclear ruthenium system, which contains easily dissociated ligand p-cymene and large phosphine ligand that stabilizes the metal complex. And the possible mechanism for the reaction was proposed.

Ruthenium Ring‐Opening Metathesis Polymerization Catalysts Bearing o‐ Aryloxide‐N‐Heterocyclic Carbenes

AbstractA series of o‐aryloxide‐N‐heterocyclic carbene ruthenium complexes 2–4 is synthesized via sequential reactions of the o‐hydroxyaryl imidazolium proligands (2‐OH‐3,5‐tBu2C6H2)(R)(C3H3N2)+Br− (R = Me (1a), iPr (1b), Mes (1c)) with Ag2O and [(C6H6)RuCl2]2. All of the complexes are characterized by 1H and 13C NMR spectroscopy, high‐resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of 2 is determined by single‐crystal X‐ray diffraction analysis. The ring‐opening metathesis polymerization (ROMP) of norbornene (NBE) with 2–4 is studied. Among them, complex 4 exhibits the highest activity and efficiency toward ROMP of NBE at 85 °C without any cocatalyst, and the resultant polymers have very high molecular weight (>106 Da) and narrow molecular weight distributions. This complex can also efficiently catalyze the alternating copolymerization of NBE and cyclooctene.

Synthesis, Structures, and Norbornene ROMP Behavior of o-Aryloxide-N-Heterocyclic Carbene p-Cymene Ruthenium Complexes

Treatment of the o-hydroxyaryl imidazolium proligands (2-OH-3,5-tBu2C6H2)(R)(C3H3N2)+Br– (R = iPr (1a), tBu (1b), Ph (1c), Mes (1d)) with 3 equiv of Ag2O afforded the corresponding silver complexes 2a–d. The subsequent metal-exchange reactions with [(p-cymene)RuCl2]2 at room temperature yielded the desired o-aryloxide-N-heterocyclic carbene p-cymene ruthenium complexes 3a–d in nearly quantitative yields. All the complexes were characterized by 1H and 13C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of complex 3b was determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with 3a–d was studied. Among them, complex 3d showed high activity and efficiency toward ROMP of NBE at 85 °C without the need for any cocatalyst, and polymers with very high molecular weight (>106) and narrow molecular weight distributions were obtained. This complex can also catalyze the alternating copolymerization of NBE and cyclooctene (COE).

Ring-Opening Polymerization of THF by Aryloxo-Modified (Imido)vanadium(V)-alkyl Complexes and Ring-Opening Metathesis Polymerization by Highly Active V(CHSiMe3)(NAd)(OC6F5)(PMe3)2

Ring-opening polymerizations of THF using V(NR)(CH2SiMe3)(OAr)2 [R = 2,6-Me2C6H3, 1-adamantyl (Ad), Ph; Ar = 2,6-Me2C6H3, C6F5] proceeded in a living manner in the presence of [Ph3C][B(C6F5)4], affording high molecular weight polymers with low PDI (Mw/Mn) values: the observed activity (initiation efficiency) was affected by the arylimido and aryloxo ligands employed. A new vanadium(V)-alkylidene, V(CHSiMe3)(NAd)(OC6F5)(PMe3)2, prepared from V(NAd)(CH2SiMe3)2(OC6F5) by α-hydrogen elimination in n-hexane in the presence of PMe3 at 25 °C, exhibited remarkable catalytic activity for ring-opening metathesis polymerization of norbornene: the activity at 25 °C was higher than those by the reported vanadium(V)-alkylidenes and ordinary Mo(CHCMe2Ph)(N-2,6-iPr2-C6H3)(OtBu)2.

Structurally Characterized Cationic Silver(I) and Ruthenium(II) Carbene Complexes of 1,2,3-Triazol-5-ylidenes

A novel 1,3,4-substituted 1,2,3-triazolium salt was found to function as an effective precursor for the synthesis of the first structurally characterized cationic silver(I) and ruthenium(II)carbene complexes of overall 1:2 ligand-to-metal stoichiometry. The Ag(I) complex crystallized in the form of an eight silver atom-containing cluster, whereas the Ru(II) complex proved to be a discrete species and was found to be capable of initiating the ring-opening metathesis polymerization of norbornene upon activation with (trimethylsilyl)diazomethane.

Non-innocent Character of Oxyanions in Ruthenium Metathesis Catalysts

The synthesis, characterization, reactivity, and selectivity of six novel ruthenium metathesis catalysts containing oxyanions as ligands are described. A drop in chemoselectivity and/or reactivity in alternating ring-opening metathesis polymerization of norbornene and cyclooctene for catalysts with nitrate, acetate, and benzoate ligands (i.e., catalysts 7, 8, and 10a) compared to the parent complex bearing chloride as a ligand (5b) is observed, while catalysts with trifluoroacetate, methylbenzoate, and triisopropylbenzoate ligands (i.e., catalysts 9, 10b, and 10c) exhibit the expected activities and chemoselectivities. A model accounting for the aforementioned observations is based on a chelating effect of oxyanion ligands in these complexes and is supported by NMR data, crystal structures of the new complexes, and DFT calculations. Through comparison of selectivity and reactivity in copolymerizations with NMR and X-ray structures, we have uncovered correlations that serve as predictive tools for catalyst design.

Synthesis of (adamantylimido)vanadium(V)-alkyl complexes containing aryloxo ligands and their use as the catalyst precursors for ring-opening metathesis polymerization of norbornene, and ring-opening polymerization of tetrahydrofuran

Various (adamantylimido)vanadium(V) dialkyl complexes containing aryloxo ligands, V(NAd)(CH 2SiMe 3) 2(OAr) [Ad = 1-adamantyl ( 1); Ar = Ph ( a), 4-FC 6H 4 ( b), 2,6-F 2C 6H 3 ( c), 2,6-Me 2C 6H 3 ( d), C 6F 5 ( e)], have been prepared and identified. These complexes were employed as the catalyst precursors for ring-opening metathesis polymerization (ROMP) of norbornene (NBE) in the presence of PMe 3 at 80 °C. The activity was strongly affected by the aryloxo substituent and increased in the order: C 6H 5 < 4-FC 6H 4 < 2,6-Me 2C 6H 3 << 2,6-F 2C 6H 3, C 6F 5. The same trend was observed in the ROMPs by the arylimido–aryloxo analogues, V(NAr′)(CH 2SiMe 3) 2(OAr) ( 2a– e; Ar′ = 2,6-Me 2C 6H 3), under the same conditions, and the activities by the arylimido analogues were generally higher than the adamantylimido analogues in most case. The (imido)vanadium(V) complexes containing O-2,6-F 2C 6H 3 ( 1, 2c) or OC 6F 5 ( 1, 2e) exhibited high catalytic activities, and these results strongly suggest that electronic as well as steric factors play a role. Living ring-opening polymerization of THF proceeded in the presence of V(NAd) (CH 2SiMe 3)(OAr) 2 (Ar = 2,6-Me 2C 6H 3, C 6F 5) and [Ph 3C][B(C 6F 5) 4], affording high molecular weight polymers with narrow molecular weight distributions (ex. M n = 2.11 × 10 5, M w / M n = 1.18).

(Imido)vanadium Complexes as Efficient Catalyst Precursors for Olefin Polymerization/Oligomerization

(Arylimido)vanadium(V) complexes containing anionic ancillary donor ligands of type, V(NAr)Cl2(L) (Ar = 2,6-Me2C6H3, L = aryloxo, ketimide phenoxyimine, etc.) exhibited high catalytic activities for ethylene polymerization in the presence of Al cocatalyst; V(NAr)Cl2(O-2,6-Me2C6H3) showed the exceptionally high activities in the presence of halogenated Al alkyls such as Et2AlCl, EtAlCl2, etc. (Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe3)(NAr)(L′) (L′ = N=C t Bu2, O-2,6- i Pr2C6H3) exhibited the remarkable catalytic activities for ring-opening metathesis polymerization of norbornene. (Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl2[2-Ar′NCH2(C5H4N)] (R = 1-adamantyl, cyclohexyl, phenyl, Ar′ = 2,6-Me2C6H3, 2,6- i Pr2C6H3), exhibit the remarkable activities for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity, and the electronic nature directly affects the activity.

RuCl 2( p-cymene)(PCy 3) immobilized on mesoporous molecular sieves as catalyst for ROMP of norbornene and its derivatives

New heterogeneous catalysts for ring opening metathesis polymerization (ROMP) have been prepared by immobilization of RuCl 2( p-cymene)(PCy 3) (Cy = cyclohexyl) on silica and siliceous mesoporous molecular sieves SBA-15 and MCM-41. Activity of these catalysts was investigated in ROMP of norbornene (NBE) and its derivatives (dicyclopentadiene, 5-norbornene-2-yl acetate). High molecular weight polymers ( M w up to 400 000) were prepared in yields up to 80% using catalysts based on mesoporous sieves. In contrast, with catalyst based on conventional silica the yield did not exceed 28% (ROMP of NBE). Filtration test proved that the catalytic activity was bound to the solid phase. Catalysts could be easily separated from the reaction mixture in contrast to the corresponding homogeneous system. Therefore, polymers with reduced amounts of catalyst residues were obtained.

Vinyl and ring-opening metathesis polymerization of norbornene with novel half-sandwich iridium(iii) complexes bearing hydroxyindanimine ligands

Half-sandwich iridium complexes bearing hydroxyindanimine ligands were synthesized and employed as catalysts for the ROMP and vinyl-type polymerization of norbornene in the presence of methylaluminoxane (MAO).

Surface initiated ring-opening metathesis polymerization of norbornene onto Wang and Merrifield resins

Merrifield and Wang resins were successfully converted to supported vinyl-functionalized solid supports with excellent yields by reacting the Cl or OH functionality with an α,ω-difunctional spacer bearing a carboxylic acid group and a terminal alkene. The ruthenium initiator (PCy 3) 2Cl 2Ru = CHPh (Grubbs I catalyst) was then immobilized on the resins via cross metathesis (alkylidene exchange) and was used to initiate ROMP of norbornene. Number-average molecular weight and polydispersity index of the grafted polymers were determined after cleavage of the ester link between the resin and the spacer. The results showed a competition between ROMP and intramolecular “ring-closing” metathesis and/or intermolecular “cross” metathesis, which leads to an overestimated ruthenium initiator loading.

Efficient ring-opening metathesis polymerization of norbornene by vanadium-alkylidenes generated in situ from V(NAr)Cl 2(L) (L: ketimide, aryloxo)

Ring-opening metathesis polymerization (ROMP) of norbornene (NBE) using a catalyst system consisting of V(N-2,6-Me 2C 6H 3)Cl 2(N = C t Bu 2) ( 1a), MeMgBr, and PMe 3 proceeded at a remarkable rate, and the catalytic activities (TON values, TON = turnover number) were low when MeLi or AlMe 3 was used in place of MeMgBr. The activities increased upon increasing the polymerization temperature, and were dependent upon the molar ratio(s) of the catalyst component(s) employed. The resultant polymers prepared at 25 °C under the optimized conditions possessed high molecular weights with unimodal molecular weight distributions ( M n = 1.31–1.66 × 10 6, M w/ M n = 1.40–1.59), and contained a mixture of cis/ trans olefinic double bonds. The effects of anionic donor ligands (L) and substituents on the arylimido ligands on the activity in the ROMP using V(NAr)Cl 2(L) [Ar = 2,6-Me 2C 6H 3 ( 1), 2,6- i Pr 2C 6H 3 ( 2); L = N = C t Bu 2 ( a), N = C(CH 2SiMe 3) t Bu ( b), O-2,6-Me 2C 6H 3 ( c), O-2,6- i Pr 2C 6H 3 ( d), O-2,6- t Bu 2-4-MeC 6H 2 ( e)]-MeMgBr-PMe 3 were explored; both 1a and 1c showed the remarkable activities, and the observed trends were similar to those observed in ethylene polymerization using V(NAr)Cl 2(L)-MAO catalyst systems.

Synthesis and structure of stable cis-dimethyl complex of oxotungsten(VI)

Oxotungsten(VI) complex cis-[WO(L tBu )Me 2] (L tBu = methylamino- N, N-bis(2-methylene-4-methyl-6- tert-butylphenolate) dianion) was prepared by the transmetallation reaction of [WO(L tBu )Cl 2] (either cis or trans isomer) with methyl magnesium iodide. This unexpectedly stable dialkyl complex can be activated by Et 2AlCl to catalyze the ring-opening metathesis polymerization of norbornene.

Hepta-coordinate halocarbonyl molybdenum(II) and tungsten(II) complexes as heterogeneous polymerization catalysts

[MX 2(CO) 3(DAB)] (M = Mo, W; X = I, Br) ( 5– 8) complexes bearing the 1,4-diazobutadiene (DAB) ligand RN C(Ph) C(Ph) NR [R = (CH 2) 3Si(OEt) 3] were immobilized in MCM-41 mesoporous silica. The tethering, stepwise procedure started with treatment of the MCM-41 mesoporous material with a toluene solution of the 1,4-diazobutadiene ligand, under reflux. The molybdenum and tungsten organometallic cores were subsequently introduced into the ligand-silicas by pore volume impregnation of a solution of the complexes [MX 2(CO) 3(NCMe) 2] (M = Mo, W; X = Br, I). The modified materials were extensively characterized by several techniques, such as FTIR, solid-state MAS and CP MAS NMR ( 13C, 29Si), powder XRD, and nitrogen adsorption–desorption measurements. These new materials (containing 2.6–2.9 wt.% Mo or 0.4–0.6 wt.% W) catalyze the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene at 328 K, in contrast with the very low activity exhibited by the precursor complexes and with their behavior at lower temperature. Addition of AlCl 3 as a co-catalyst enhanced the catalytic performance of the material MCM-DAB-MoBr 2 ( 12) in the ROMP of NBE.

Photochemical reaction of W(CO) 6 with GeCl 4 as a source of germyl and germylene compounds acting as initiators for ring-opening metathesis polymerization of norbornene

Photolysis of W(CO) 6 in a solution of n-heptane containing GeCl 4 leads to the formation of two seven-coordinate compounds with direct W Ge bonds: [(CO) 4W(μ-Cl) 3W(GeCl 3)(CO) 3] ( 1) and [(μ-GeCl 2){W(CO) 5} 2] ( 2). The molecular structures of these two tungsten–germanium compounds have been established by single-crystal X-ray diffraction studies. The germyl compound 1 is a previously synthesized binuclear complex of tungsten(II) with a d 4 electronic configuration, while in the new germylene compound 2 the tungsten atom is formally in the zero oxidation state with a d 6 electronic configuration and a direct W W bond. In an attempt to establish whether compounds 1 and 2 could be used as precatalysts for the ring-opening metathesis polymerization (ROMP) of cyclic olefins, their reactivity towards norbornene has been studied. In chloroform- d 1 solution the ROMP reaction is accompanied by the formation of a new olefin, 2,2′-binorbornylidene (bi-(NBE)), as a result of carbene–carbene coupling. In reaction of norbornene carried out in benzene solution the ROMP reaction is accompanied by the formation of 2-phenylnorbornane (hydroarylation product) and small amounts of bi-(NBE). In general, in the presence of olefin, compound 2 undergoes rearrangement to give an olefin compound of the type [(WCO) 5(η 2-olefin)].

Sequential Electrografting and Ring‐Opening Metathesis Polymerization: a Strategy for the Tailoring of Conductive Surfaces

AbstractSummary: An electrografting technique has been combined with ring‐opening metathesis polymerization (ROMP). Poly(allyl methacrylate) chains have been chemisorbed onto steel and carbon plates under an appropriate cathodic potential in N,N‐dimethylformamide. The allyl moieties have been converted into Ru catalysts active in ROMP of norbornene and its derivatives. Initiation of ROMP from the surface is an efficient strategy to prepare strongly adhering coatings of tunable thickness and hydrophilic/hydrophobic balance, depending on the norbornene derivative polymerized at the surface.The hydrophobicity of the polymer coating may be controlled by hydrolysis of the polynorbornene derivative.magnified imageThe hydrophobicity of the polymer coating may be controlled by hydrolysis of the polynorbornene derivative.

Application of electrochemically generated molybdenum-based catalyst system to the ring-opening metathesis polymerization of norbornene and a comparison with the tungsten analogue

This study describes the application of the electrochemically generated molybdenum-based catalyst system MoCl5e−AlCH2Cl2 to ring-opening metathesis polymerization of bicyclo[2.2.1]hept-2-ene (norbornene). The results are compared with those previously obtained by the WCl6e−AlCH2Cl2 system. The polymer product has been characterized by 1H and 13C NMR, IR and gel-permeation chromatography techniques. This molybdenum-based catalyst system has led to a mainly trans stereoconfiguration (ca 60%) of the double bonds, in contrast to the polymer obtained with the tungsten-based analogue, where the cis content is 60%. Analysis of the poly(1,3-cyclopentylenevinylene) microstructure by 13C NMR spectroscopy revealed that the polymer having σc = 0.41 (fraction of double bonds with cis configuration) contains a slightly blocky distribution (rtrc > 1) of the double-bond dyads (rtrc = 1.44). In addition, the influence of reaction parameters, e.g. reaction time, electrolysis time and catalyst aging time, on conversion has been analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd.

Unexpected Volume Expanding Behavior on Ring-Opening Metathesis Polymerization of Norbornene Bearing a Five- or Six-Membered-Ring Cyclic Carbonate Followed by a Cationic Ring-Opening Cross-Linking Reaction

Unexpected Volume Expanding Behavior on Ring-Opening Metathesis Polymerization of Norbornene Bearing a Five- or Six-Membered-Ring Cyclic Carbonate Followed by a Cationic Ring-Opening Cross-Linking Reaction

Tungsten(VI) complexes with aminobis(phenolato) [O,N,O] donor ligands.

The reaction between trisdiolatotungsten(VI) complex [W(eg)(3)] (1) (eg = 1,2-ethanediolato dianion) and phenolic ligand precursor methylamino-N,N-bis(2-methylene-4,6-dimethylphenol) (H(2)L(Me)) or methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol) (H(2)L(tBu)) affords monomeric oxotungsten complex [WO(eg)(L(Me))] (2) or [WO(eg)(L(tBu))] (3), respectively. These complexes react further with chlorinating reagents, which leads to the displacement of ethanediolato ligands from the complex units and formation of cis and trans isomers of the corresponding dichloro complexes [WOCl(2)(L(Me))] (4) and [WOCl(2)(L(tBu))] (5), respectively. Identical dichloro complexes were also prepared by the reaction between the above-mentioned phenolic ligand precursors and [WOCl(4)]. Molecular structures of 3, cis-4, trans-4, and cis-5 were verified by X-ray crystallography. Complexes 2-5 can be activated by Et(2)AlCl to catalyze ring-opening metathesis polymerization of norbornene.

Preparation and Utilization of Catalyst-Functionalized Single-Walled Carbon Nanotubes for Ring-Opening Metathesis Polymerization

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.