Polymerization Of Norbornene Research Articles

Dual catalytic performance of arene‐ruthenium amine complexes for norbornene ring‐opening metathesis and methyl methacrylate atom‐transfer radical polymerizations

Arene ruthenium(II) complexes bearing the cyclic amines RuCl2(η6‐p‐cymene)(pyrrolidine)] (1), [RuCl2(η6‐p‐cymene)(piperidine)] (2), and [RuCl2(η6‐p‐cymene)(peridroazepine)] (3) were successfully synthesized. Complexes 1–3 were fully characterized by means of Fourier transform infrared, UV–visible, and NMR spectroscopy, elemental analysis, cyclic voltammetry, computational methods, and one of the complexes was further studied by single crystal X‐ray crystallography. These compounds were evaluated as catalytic precursors for ring‐opening metathesis polymerization (ROMP) of norbornene (NBE) and atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA). NBE polymerization via ROMP was evaluated using complexes 1–3 as precatalysts in the presence of ethyl diazoacetate (EDA) under different [NBE]/[EDA]/[Ru] ratios, temperatures (25 and 50°C), and reaction times (5–60 min). The highest yields of polyNBE were obtained with [NBE]/[EDA]/[Ru] = 5000/28/1 for 60 min at 50°C. MMA polymerization via ATRP was conducted using 1–3 as catalysts in the presence of ethyl‐α‐bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] = 1000/2/1 at 95°C. The increase in molecular weight as function of time indicates that complexes 1–3 were able to mediate the MMA polymerization with an acceptable rate and some level of control. Differences in the rate of polymerization were observed in the order 3 > 2 > 1 for the ROMP and ATRP.

Bis(N-acylated imidazolin-2-imine) nickel catalyzed norbornene copolymerization with methyl acrylate

We herein report the synthesis of novel bis(N-acylated imidazolin-2-imine) nickel complexes for norbornene polymerization and copolymerization with polar monomers.

Cooperative Effects of Aniline with DMSO in RuII Complexes: Tuning the Reactivity for Ring‐Opening Metathesis Polymerization

The complex cis,fac‐[RuCl2(DMSO–O)(DMSO–S)3] [1] reacted with aniline (NH2Ph) under reflux to produce the complex trans,cis,cis‐[RuCl2(DMSO–S)2(NH2Ph)2] [2], whereas at room temperature the resulting complex was cis,fac‐[RuCl2(DMSO–S)3(NH2Ph)] [3]. The complexes were characterized by FTIR, EPR, 1H and 13C NMR, electronic spectra, and the crystal structure of 2 was determined by single X‐ray crystallography. The influence of NH2Ph and DMSO as ancillary ligands in the new complexes was then evaluated for ring‐opening metathesis polymerization (ROMP) of norbornene (NBE), norbornadiene (NBD), and dicyclopentadiene (DCPD) in presence of ethyl diazoacetate (EDA) with different [monomer]/[Ru] molar ratios. Homopolymers of NBE with molecular weights in the order of magnitude of 105 g.mol–1 and insoluble polymers in CHCl3 from NBD and DCPD were obtained in different yields depending of the starting complex, reaction time (5 and 30 min), and temperature (25 and 50 °C). Valorous results were obtained for polyNBD, polyDCPD, and copolymerizations from NBE with NBD or DCPD using the new complexes, affording higher yields than with 1. In conclusion, beneficial effects are observed when DMSO and the weak σ‐donor NH2Ph ligands are arranged in the same coordination sphere of Ru(II) pre‐catalysts for ROMP.

Synthesis and Catalytic Properties of Cyclopalladated Complexes Bearing a Phosphane‐Sulfonate Ligand

Reactions of the phosphane‐sulfonate ligand with [Pd(OAc)(8‐Me‐quin‐H)]2 or [Pd(dmba)(µ‐Cl)]2 (dmba = Me2NCH2C6H5) in acetonitrile afforded the corresponding C(sp3),N‐chelated palladacycle Pd1 and C(sp2),N‐chelated palladacycle Pd2 in high yields. Both complexes have been fully characterized by 1H and 13C NMR, high‐resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of Pd1 was further confirmed by single‐crystal X‐ray diffraction analysis. With Et2AlCl as cocatalyst, these complexes showed moderate catalytic activities for the addition polymerization of norbornene. While with methylaluminoxane (MAO) as cocatalyst, they showed high catalytic activities (up to 5.80 × 107 g of PNB (mol of Pd)–1 h–1) at higher temperatures (above 100 °C). The C(sp3),N‐chelated palladacycle Pd1 exhibited marked higher activities than the C(sp2),N‐chelated palladacycle Pd2, whether Et2AlCl or MAO was used as cocatalyst.

Synthesis of Poly(norbornene) Anion Conducting Membranes for Alkaline Electrochemical Devices: Structure-Property Relationships

Anion-exchange membranes (AEMs) are used in electrochemical energy storage and conversion devices such as batteries, fuel cells, and electrolyzers. The development of AEMs with long-term alkaline stability and high anion conductivity (i.e. hydroxide, carbonate and bicarbonate) is of current interest. The benefits over proton-exchange membrane (PEM) devices include the use of non-precious catalysts, facile reaction kinetics, and reduced fuel crossover. However, the issues with the low ionic conductivity, poor stability at high pH, and high water uptake are need to be addressed. A series of homopolymers and block copolymers containing non-hydrolysable backbone and long-chain head-group tethers based on vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes were synthesized for use in AEM fuel cells. The focus of this talk is on the structure-property relationships of poly(norbornene) anion exchange membranes. Polymers were cross-linked with N,N,N′,N′-Tetramethyl-1,6-hexanediamine (TMHDA) to control the water uptake, and improve the mechanical properties. The structure property relationship of AEMs towards high ionic conductivity was correlated with ion-exchange capacity (IECs), number and size of the blocks, molecular weight, and polydispersity. The membranes had record high conductivity of 212 mS/cm at 80 °C and low water uptake. The long-term alkaline stability showed <1% conductivity loss in over 1200 h at 80 °C. The membranes have been used in anion-exchange membranes fuel cells and electrolyzers.

Norbornene Addition Polymerization with Catalysts Based on Transition Metal Compounds: 2008–2018

This review summarizes the data on the addition polymerization of norbornene catalyzed by various transition metal complexes published over the period of 2008–2018. The interest in the addition polynorbornenes is due to their dielectric, mechanical, and optical properties, which makes them attractive for use in the microelectronic industry and optics. The regularities of polymerization using catalysts based on Ti, Ir, Ni, Pd, and Cu compounds are considered.

Placing single monomers in a polymer

A new method allows chemists to precisely place single monomers at any position within a polymer chain made of other types of monomers. With this single monomer, chemists can add various types of functionality, such as chromophores to produce sensors or another polymer chain to create novel polymer architectures. Previous methods for adding single monomers have lacked precision, adding either multiple monomers or none where only one was desired. In the new method, Yan Xia and coworkers at Stanford University use cyclopropene ester derivatives with ring-opening metathesis polymerization to add individual cyclopropenes at multiple locations in a polymer otherwise made from norbornenes (Chem 2019, DOI: 10.1016/j.chempr.2019.07.017). For examples, if they want to make a 100-unit polymer with the special monomer at about 30% of the total length, they first make a 30-unit polymer and then add the cyclopropene monomer. They then continue the norbornene polymerization with another 70-unit segment. The

Precise Placement of Single Monomer Units in Living Ring-Opening Metathesis Polymerization

Summary Precise control of the location and sequence of monomers in a narrow-disperse polymer chain remains a significant challenge. Our strategy uses selective and quantitative single additions of cyclopropene (CPE) derivatives to precisely place functional moieties at desired locations along a polymer chain during the living ring-opening metathesis polymerization (ROMP) of norbornenes (NBEs). In order to completely reinitiate the chain end after single addition of a CPE, we lowered the reaction temperature and added a labile ligand. Under our optimized conditions, we demonstrated the exclusive placement of single moieties at pre-determined locations along a polynorbornene (PNBE) homo or block co-polymer while maintaining narrow MW distributions and controlled MWs. Some polymers were used to synthesize precisely controlled branched architectures. The ability to control the location and number of individual functional groups in a polymer chain opens exciting opportunities for the precise synthesis and manipulation of polymer structures, architectures, assemblies, and properties.

(Arylimido)vanadium(V)-Alkylidene Complexes as Catalysts for Ring-opening Metathesis Polymerization (ROMP) of Cyclic Olefins: Ligand Design for Exhibiting the High Activity

(Imido)vanadium(V)-alkylidene complexes of type V(CHSiMe3)(NR)(OR′)(PMe3)2 [R = Ad, C6H5, 2,6-Me2C6H3, 2,6-Cl2C6H3; R′ = 2,6-Me2C6H3, 2,6-iPr2C6H3, 2,6-F2CeH3, C6F5, C6Cl5] exhibited from moderate to remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene (NBE). The catalytic activities were affected by the ligand substituents, and V(CHSiMe3)(N-2,6-Cl2C6H3)(OC6X5)(PMe3)2 (X = F, Cl) demonstrated the exceptionally high catalytic activities for ROMP of NBE. The complexes polymerized cycloheptene (CHPE) and cis-cyclooctene (COE), and ROMP of COE by the OC6Cl5 analogue proceeded in a living manner even at 80 °C, and the activity increased with increasing the temperature up to 120 °C. Highly active catalysts for ROMP of cyclic olefins (NBE, cyclopentene, and CHPE) can be generated in situ by premixing isolated V(CHSiMe3)(NC6F5)(O-2,6-iPr2C6H3)(PMe3)2 with 1.0 equiv. of C6F5OH or C6Cl5OH via immediate phenoxy exchange; the activity was affected by the kind of phenol added [TOF in the ROMPs of NBE: 4.62 × 104 min−1 (upon addition of C6F5OH) versus 37.3 min−1 (none)].

Efficient Addition Polymerization of Norbornene with Polar Norbornene Derivatives by Neutral Nickel(II) Catalysts

A series of nickel complexes {4a: [(2,6-iPr2C6H3)N=CHC16H12O]Ni(Me)(Py), 4b: [(2,6-iPr2C6H2OCH3)N=CHC16H12O]-Ni(Me)(Py), 4c: [(2,6-iPr2C6H2Cl)N=CHC16H12O]Ni(Me)(Py), and 4d: [(2,6-iPr2C6H2CF3)N=CHC16H12O]Ni(Me)(Py)} based on β-ketiminato ligands bearing various electron-donating or electron-withdrawing substituents on the para-position of the aniline group were synthesized and unambiguously characterized. The X-ray crystallographic analysis showed that complexes 4b and 4d adopted a near-square-planar geometry, and the anilines bearing a para-OMe or −CF3 group were found to situate on the axial position of the metal center. All complexes exhibited high activities up to 1.25 × 107–1.35 × 107 gPNB·molNi−1·h−1 toward norbornene (NBE) addition polymerization (conversion > 91.2% in 2 min) under low loading of B(C6F5)3 (B/Ni = 3) at 30 °C, affording polymers with high molecular weight up to 2.54 × 106–3.18 × 106. Different levels of decrease in catalytic activities could be observed for all catalysts as the reaction temperature increased; 4d bearing a strong electron-withdrawing −CF3 group showed the highest activity at 70 °C, while others exhibited notable decrease in catalytic activity with the raise in reaction temperature. Complexes 4a–4d showed remarkable tolerance to polar groups and could efficiently promote the copolymerization of NBE with its polar derivatives, including NBE bearing small acetate and hydroxyl group, as well as bulky oligomers, yielding copolymers with high functional NBE incorporations. Novel NBE copolymers with high functional comonomer incorporations and improved solubility were obtained in high yields.

Synthesis of Novel Palladium Complexes Containing β‐Diketonate and NHC Ligands and their Catalytic Ability for Addition Polymerizations of the Functional Norbornenes

Palladium complexes containing various N‐heterocyclic carbene (NHC) ligands have been successfully synthesized by the reaction with various β‐diketonate complexes. Treatments of Pd(acac)2 with NHC salts such as 1,3‐di(2,6‐diisopropylphenyl)imidazolium chloride (IPr·HCl) or 1,3‐di(mesityl)imidazolium chloride (IMes·HCl) resulted in [Pd(acac)(NHC)Cl] complexes and these complexes were characterized by NMR. Moreover, these palladium complexes showed moderate to good catalytic activities towards addition polymerization of various functional norbornenes. The effects of various reaction parameters onto the catalytic activity towards polymerization of functional norbornenes have been thoroughly investigated.

(Invited) High Conductivity, Stable Anion Conducting Membranes Based on Poly(norbornene)

Alkaline exchange membranes (AEM) fuel cells and electrolyzers are potentially cost-saving alternatives to traditional proton exchange membrane (PEM) devices. Recently, anion conducting polymer membranes have achieved ionic conductivity and chemical stability comparable to Nafion, the current state of the art in PEM technology. Phase segregation is an effective way to achieving high hydroxide mobility. An all-carbon backbone with light cross-linking and a long, alkyl tether for the cation head-group are effective means of achieving chemical stability and limiting unwanted water hydration. In this study, a series of tetrablock copolymers containing an all-hydrocarbon backbone and tethered quaternary ammonium groups were synthesized based on vinyl addition polymerization of norbornene. Several variations of block copolymer AEMs with different ion exchange capacities (IEC) were made by adjusting the ratio of hydrophilic to hydrophobic blocks. Correlations were found between the ionic conductivity and mechanical properties to the polymer structure, channel size, and degree of phase separation. Furthermore, it was found that light crosslinking of the membranes allows for high IEC materials to be used while maintaining acceptable water uptake. The crosslinked AEMs have demonstrated record-high hydroxide conductivities (198 mS/cm) for a chemically stable polymer. The chemical degradation at 80oC in 1 M KOH was <1% degradation in 1,200 hours. The AEMs were also used to construct MEAs for alkaline fuel cells.

High Tg and thermostable phytic Acid−Cured polynorbornene-based polymer by a Palladium(Ⅱ) complex bearing iminophenyl oxazolinylphenylamines ligand

Fabrication of thermosets with high glass transition temperature (Tg) has been a challenge in recent years. In this study, a facile method is presented to prepare high Tg polymers with good thermostability. Firstly a chiral palladium (II) complex bearing an iminophenyl oxazolinylphenylamine (IPOPA) ligand, IPOPA-PdCl, has been prepared and characterized, which exhibits high activities for vinyl-(co)polymerization of norbornene (NB) and 5-vinyl-2-norbornene (VNB) in the presence of various cocatalysts. Then the synthesized copolymer P(NB-vinylNB) is epoxidized to generate epoxy product P(NB-epoxyNB). Phytic acid (PA), which is a naturally component in plants, is then used to cross-link P(NB-epoxyNB) for further restricting molecular motions. The obtained crosslinked P(NB-epoxyNB)-PA exhibits high Tg of up to 351.5 °C. This work not only provides insight into the design of novel semi-salen type palladium (II)-based catalyst for vinyl-(co)polymerization of NB and its derivative, but also shows a feasible strategy to design thermosetting PNB-based polymer with high Tg and thermostability.

Highly Conductive Anion-Exchange Membranes Based on Cross-Linked Poly(norbornene): Vinyl Addition Polymerization

Cross-linked (XL) anion-exchange membranes (AEMs) synthesized by vinyl addition polymerization of norbornene were prepared for use in anion-exchange membrane electrochemical devices, including fuel...

Vinylic Addition Polynorbornene in Catalysis

AbstractVinylic addition polynorbornenes (VA‐PNB) result from the insertion polymerization of norbornene or specific norbornene derivatives catalyzed by transition metal complexes. The VA‐PNB skeleton is completely aliphatic and keeps the bicyclic structure of norbornene. This saturated polymer is thermally and chemically very stable and it is a very robust scaffold to support catalysts or reagents for catalytic applications. Several VA‐PNBs are now available with suitable functional groups (halogen, alkenyl, carbonates) that can be used as starting materials to introduce the functionalization of choice by post‐polymerization reactions. This has been applied to anchor organocatalysts on VA‐PNB as well as ligands that can be used to synthesize supported metal catalysts. The reported examples of the use of VA‐PNB‐linked catalysts and their recyclability will be presented. VA‐PNBs have also proved useful in the context of organotin chemistry to solve the problem of tin contamination by an efficient separation and the reuse of tin byproducts. Its uses in the Stille cross‐coupling reaction and tin‐hydride radical processes will be discussed.

Nickel(II) and Palladium(II) Complexes Bearing an Unsymmetrical Pyrrole-Based PNN Pincer and Their Norbornene Polymerization Behaviors versus the Symmetrical NNN and PNP Pincers.

Unsymmetrical pincers have been shown to be better than the corresponding symmetrical pincers in several catalysis reactions. A new unsymmetrical PNN propincer, 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole (1), was synthesized from pyrrole through Mannich bases in a good yield. In addition, the new byproduct 2-(3,5-dimethylpyrazolylmethyl)-5-(dimethylaminomethyl)- N-(hydroxymethyl)pyrrole was also isolated. The reaction of 1 with [PdCl2(PhCN)2] and Et3N in toluene yielded [PdCl{C4H2N-2-(CH2Me2pz)-5-(CH2PPh2)-κ3 P,N,N}] (2). The analogous reaction between 1 and [NiCl2(DME)] or NiX2 (X = Br, I) in the presence of NEt3 in acetonitrile afforded [NiX{C4H2N-2-(CH2Me2pz)-5-(CH2PPh2)-κ3 P,N,N}] (3; X = Cl, Br, I). All complexes were structurally characterized. The norbornene polymerization behaviors of the unsymmetrical pincer complexes 2 and 3 in the presence of MMAO or EtAlCl2 were compared with those of the symmetrical pincer complexes chloro[2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrolido]palladium(II) (NNN), chloro[2,5-bis(diphenylphosphinomethyl)pyrrolido]palladium(II), and chloro[2,5-bis(diphenylphosphinomethyl)pyrrolido]nickel(II) (PNP) at different temperatures. The PNN and NNN complexes exhibited far greater activity on the order of 107 g of PNB/mol/h, with quantitative yields in some cases, in comparison to the PNP pincer palladium and nickel complexes. This trend was also supported by the iPr group substituted PNP nickel and palladium pincer complexes. These polymerization behaviors are explained using steric crowding around the metal atom with the support of NMR studies and suggested that the activity increases as the Npyrazole donor increases. Polymers were characterized by 1H NMR, IR, TGA, and powder XRD methods.

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials.

This mini-review summarizes the applications of olefin metathesis in synthesis and functionalization of polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials. Three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis polymerization (ROMP) of POSS-substituted norbornene (or other ROMP susceptible cycloolefins) are discussed. Emphasis was put on the synthetic and catalytic aspects rather than on the properties and applications of synthesized materials.

Tridentate diarylamido-based pincer complexes of nickel and palladium: sidearm effects in the polymerization of norbornene.

Nickel and palladium complexes bearing new diarylamido-based unsymmetrical [NNNox] and [SNNox] pincer ligands were synthesized and tested for the polymerization of norbornene. Upon the activation of MAO, all the palladium complexes showed high catalytic activities for the vinyl-addition polymerization of norbornene up to 5.32 × 107 g of PNB (mol of Pd)-1 h-1, while the corresponding nickel complexes exhibited unsatisfactory catalytic activities. Besides the usual steric and electronic effects, the sidearm effects of quinolino ([NNNox] ligands) and phenylthio ([SNNox] ligands) moieties have also exhibited obvious influence on the catalytic performance for the polymerization of norbornene and were further studied by density functional theory (DFT) calculations.

Synthesis of Cationic Pd(II) Complexes with 5-Membered Ring Chelating Iminoylcarbene Ligand and Its Catalytic Activity on Norbornene Polymerization

Iminoyl N-heterocyclic carbine ligand with cationic allyl Pd(II) complex (3) was successfully synthesized by transmetallation of corresponding Ag complex with one equivalent of [Pd(allyl)(COD)]+SbF6–. A slightly distorted square planer structure of the Pd(II) complex 3 was confirmed by single crystal X-ray diffraction analysis. The Pd(II) complex 3 is stable in air and found to show moderate activity in the polymerization of norbornene without any activator. The polynorbornene produced with Pd(II) complex 3 was obtained to be stable up to 440 °C. The 1H and 13C NMR spectra of the polymer indicated addition polymerization of norbornene and the presence of the vinylene group at the end of polymer chain.

Norbornene polymerization and copolymerization with 1-alkenes by neutral palladium complexes bearing aryloxide imidazolin-2-imine ligand

A series of novel aryloxide imidazolin-2-imine bidentate neutral Pd(ii) complexes with different substituents on the imidazolin-2-imine ligand were synthesized and characterized.