Polymerization Of Norbornene Research Articles

Precision polymers: a kinetic approach for functional poly(norbornenes)

Control over monomer sequence in the ring-opening metathesis polymerization of functional norbornenes is explored based on the difference in reactivity of endo and exo isomers.

Electronicvs. Steric Hindrance Effects in Amine Ligands to Ru-Based Initiators for ROMP

[RuCl2(PPh3)2(amine)x]-type complexes, with NH2Ph (1; x = 2), NH2Bz (2; x = 2) and NHBuPh (3; x = 1) in the presence of ethyldiazoacetate (EDA), were investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE), norbornadiene (NBD) and dicyclopentadiene (DCPD). Quantitative yields of polyNBE were obtained at 50 °C for 30 min with 1 and for 5 min with 2, whereas this occurred at 25 °C for 5 min with 3. Polydispersity index (PDI) values ranged from 3.5 to 1.6 (M w = 10 4 -10 5 g mol -1 ). Complex 3 was active for ROMP of NBD and DCPD, as well as for copolymerizations of NBE with either NBD or DCPD. The high σ-donor character of NH2Bz favored the reactivity of the six-coordinated complex 2, contrary to complex 1. The large cone angle of NHBuPh defined the fivecoordination in 3 and the best reactivity for ROMP, in spite of the low σ-donor character as in NH2Ph.

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.

Synthesis, structures, and norbornene polymerization behavior of C(sp³), N-chelated palladacycles bearing o-aryloxide-N-heterocyclic carbene ligands.

Treatment of the o-hydroxyaryl imidazolium pro-ligands (2-OH-3,5-tBu2C6H2)(R)(C3H3N2)(+)Br(-) [R = Mes (1a), Ph (1b), iPr (1c), Me (1d)] with Ag2O afforded the corresponding silver complexes 2a-d. Subsequent metal-exchange reactions of 2a-d with [Pd(OAc)(8-Me-quin-H)]2 (3) yielded the desired C(sp(3)), N-chelated and o-aryloxide-NHC-ligated palladacycle complexes 4a-d in 60-80% yields. When the N-tert-butyl substituted o-hydroxyaryl imidazolium pro-ligand 1e reacted with 3 in the presence of K2CO3 in dioxane, the palladacycle complex 4e, in which the NHC adopted an abnormal binding (C4-bonding), was obtained in 20% yield. All these complexes were fully characterized using (1)H and (13)C NMR spectra, high-resolution mass spectrometry (HRMS), and elemental analysis. Single-crystal X-ray diffraction analysis results further confirmed the molecular structures of 4a-c and the abnormal binding of NHC in 4e. With methylaluminoxane (MAO) as the cocatalyst these palladacycles showed excellent catalytic activities of up to 10(7) g of PNB (mol of Pd)(-1) h(-1) in the addition polymerization of norbornene.

Vinyl polymerizations of norbornene catalyzed by nickel complexes with acetoacetamide ligands

On the basis of a remote effect, a series of acetoacetamide ligands and corresponding nickel complexes N‐(R‐phenyl) acetoacetamide Ni(CH2Ph) (PMe3) (R = H, 1; R = 2‐methyl, 2; R = 2,6‐dimethyl, 3; R = 2,6‐diisopropyl, 4; R = 4‐NO2, 5) were synthesized and characterized. The solid structure of complex 3 was confirmed by X‐ray single‐crystal analysis to be of cis form. 1H and 31P NMR spectroscopy confirmed that cis and trans isomers of nickel complexes were present in solution. Norbornene polymerizations with acetoacetamide nickel complexes activated with modified methylaluminoxane (MMAO) were investigated in detail. Remote steric and electronic effects of acetoacetamide ligand on catalytic activity and molecular weight of polynorbornenes (PNBs) were observed. Characterizations of the obtained PNBs show that the obtained polymer products are non‐crystalline vinylic‐addition polynorbornenes. Copyright © 2013 John Wiley & Sons, Ltd.

Synthesis of Polyolefin/Layered Silicate Nanocomposites via Surface-Initiated Ring-Opening Metathesis Polymerization

Here we report the synthesis and characterization of block copolymer/layered silicate (BCPLS) nanocomposites via the surface-initiated ring-opening metathesis polymerization (SI-ROMP) of norbornene and cyclopentene from montmorillonite clay (MMT). The MMT particle surfaces were functionalized with a norbornene-terminated alkylammonium surfactant through ion exchange. Block copolymer brushes of norbornene and cyclopentene were polymerized directly from the surface of these functionalized clay platelets, yielding highly exfoliated nanocomposites. A fraction of the polymer brushes were removed from their substrate by reverse ion exchange and characterized in parallel with their corresponding nanocomposite analogues. The thermal, mechanical, and morphological characteristics of the BCPLSs and their neat analogues were then compared directly. This enabled us to assess the role of the MMT filler in the thermal properties, solid/melt state rheology, and morphology.

Near-infrared (NIR) luminescent metallopolymers based on Ln4(Salen)4 nanoclusters (Ln = Nd or Yb)

A series of novel Wolf Type II Ln3+-containing metallopolymers PNBE-co-Ln4(Salen)4 (Ln = La, Nd, Yb, Er or Gd) are obtained from the controlled ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and the homoleptic tetranuclear [Ln4(L)2(HL)2Cl2(μ3-OH)2]·2Cl (Ln4(Salen)4, Ln = La, 1; Nd, 2; Ln = Yb, 3; Ln = Er, 4; Ln = Gd, 5) self-assembled from the diallyl-modified flexible hexadentate Salen-type Schiff-base ligand H2L (N,N′-bis(5-allyl-3-methoxysalicylidene)cyclohexane-1,2-diamine) with LnCl3·6H2O. The results of their photophysical properties show that the strong and characteristic near-infrared (NIR) luminescent Ln3+-centered emissions for PNBE-co-Ln4(Salen)4 (Ln = Nd, 2; Yb, 3) are retained with relatively higher intrinsic quantum yields than the corresponding monomers in solution, and the concentration self-quenching of Ln3+-based materials could be effectively prevented in both solution and solid states.

Nickel complexes bearing N,N,N-tridentate quinolinyl anilido–imine ligands: Synthesis, characterization and catalysis on norbornene addition polymerization

The N,N,N-tridentate quinolinyl anilido–imine ligands 2-(ArNC(H))C6H4–HNC9H6N (LaH, Ar = 2,6-Me2C6H3; LbH, Ar = 2,6-iPr2C6H3) and 2-(C9H6N)NC(H)C6H4–HNAr (LcH, Ar = 2,6-Me2C6H3; LdH, Ar = 2,6-iPr2C6H3) were synthesized and characterized. Reactions of these ligands with nBuLi and subsequent additions of NiCl2(DME) afford the N,N,N-tridentate nickel complexes [2-(ArNC(H))C6H4–NC9H6N]NiCl (Ar = 2,6-Me2C6H3 (1a), 2,6-iPr2C6H3 (1b)) and [2-(C9H6N)NC(H)C6H4–NAr]NiCl (Ar = 2,6-Me2C6H3 (2a), 2,6-iPr2C6H3 (2b)). All the complexes were fully characterized by NMR and elemental analyses. X-ray diffraction analyses of 1b and 2b revealed an almost square-planar geometry around the metal center. When activated with MAO, these nickel complexes can be used as catalysts for the vinyl addition polymerization of norbornene affording high molecular weight polymer.

Nickel(II) and copper(II) complexes as catalysts for norbornene vinyl polymerization bearing tetradentate β-ketoiminato ligands

The series of nickel(II) and copper(II) complexes (3a–f) bearing tetradentate [ONNO] β-ketoiminato ligands, N,N′-bis(2-benzoyl-3-oxobutylidene)-o-phenylenediamine 2a, N,N′-bis(2-benzoyl-3-oxobutylidene)-ethylenediamine 2b, N,N′-bis(2-benzoyl-3-oxobutylidene)-trans-1,2-cyclohexanediamine 2c, have been synthesized and characterized. X-ray crystal structures of complexes 3a–c and 3e–f reveal that each central metal adopts an almost square planar coordination geometry. Upon activation with methylaluminoxane (MAO), the nickel(II) complexes 3a–c display high catalytic activities for the vinyl polymerization of norbornene (NB), yielding high molecular weights of the polynorbornene (PNB), especially the complex 3b (24.46×105gPNB/molNih). While copper(II) complexes 3d–f only traces of PNB are generated. The catalytic system 3b/MAO is chosen for further investigations under various polymerization parameters.

Synthesis and Structure of Imine–N-Heterocyclic Carbene Palladium Complexes and Their Catalytic Behavior in Norbornene Polymerization

On the basis of the steric effects of ligand, a series of imine–N-heterocyclic carbene (NHC) ligands and their corresponding five-membered palladium complexes with bulky substituents on both the imine and the NHC moieties were synthesized and characterized. Transpalladation of silver carbene complexes with (COD)PdCl2 and (COD)PdMeCl afforded the palladium dichloride and methylpalladium complexes, respectively. Bulky cationic palladium complexes were further obtained by treatment of the methylpalladium complexes with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (NaBAF) in CH3CN. Well-defined cationic palladium complexes were confirmed by X-ray crystal diffraction to have trans forms. Palladium dichloride complexes and methylpalladium complexes after activation with MMAO show high activity for norbornene polymerization, whereas cationic palladium complexes can polymerize norbornene alone without any cocatalysts and exhibit a high thermostability. Norbornene polymerization with the cationic palladium catalyst was proven to proceed through a coordination–insertion mechanism by NMR studies. Analysis of oligomers obtained by polymerizing the monomer in the presence of H2 reveals the existence of a C7 linkage in the polynorbornene (PNB) by σ-bond metathesis, which may be the reason for the insolublity of polynorbornenes obtained by palladium catalysts.

Diene–iridium–tin complexes. Comparison of conjugated versus non-conjugated dienes and trimethyltin versus trichlorotin as ligands. Ring opening metathesis polymerization of norbornene by Ir(1,5-cycloocta-diene)2SnCl3

A number of bis(diene)iridium(I)tin complexes have been synthesized to assess the influence of various dienes on the steric and electronic properties of Ir(diene)2Sn(CH3)3, where the diene is DMB = 2,3-dimethyl-1,3-butadiene (1), NBD = 2,5-norbornadiene (2), or COD = cycloocta-1,5-diene (3). Comparisons are also made to a similar series, Ir(diene)2SnCl3, where the diene is DMB = 2,3-dimethyl-1,3-butadiene (4), NBD = 2,5-norbornadiene (5), or COD = cycloocta-1,5-diene (6). The syntheses of 1–5 are reported herein; the syntheses of 5 and 6 have been previously reported. The crystal structures of 1–5 have been determined by single crystal X-ray diffraction. Compounds 1–6 have been characterized by mass spectroscopy and 1H NMR spectroscopy. The olefinic protons of compounds 1–6 exhibit vicinal proton coupling to the tin center. A clear film was isolated after the exposure of norbornene to compound 6 in toluene.

End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I)-catalyzed azide–alkyne cycloaddition

Functionalizable monotelechelic polymers are useful materials for chemical biology and materials science. We report here the synthesis of a capping agent that can be used to terminate polymers prepared by ring-opening metathesis polymerization of norbornenes bearing an activated ester. The terminating agent is a cis-butene derivative bearing a Teoc (2-trimethylsilylethyl carbamate) protected primary amine. Post-polymerization modification of the polymer was accomplished by amidation with an azido-amine linker followed by Cu(I)-catalyzed azide–alkyne cycloaddition with propargyl sugars. Subsequent Teoc deprotection and conjugation with pyrenyl isothiocyanates afforded well-defined end-labeled glycopolymers.

Formation of Cationic Intermediates upon the Activation of Bis(imino)pyridine Nickel Catalysts

The activation of bis(imino)pyridine nickel(II) dichloride complexes [LNiCl2] with methylalumoxane (MAO) and AlMe3/[CPh3][B(C6F5)4] was studied by multinuclear NMR spectroscopy. Formation of similar outer-sphere ion pairs of the types [LNiMe]+[MeMAO]− and [LNiMe]+[B(C6F5)4]−, capable of promoting norbornene polymerization, was observed.

Nickel(II) and Palladium(II) Complexes with Tridentate [C,N,S] and [C,N,P] Ligands: Syntheses, Characterization, and Catalytic Norbornene Polymerization

A series of tridentate monoanionic [C–,N,X] (X = S, P) nickel(II) complexes [(C6H4CH═NPh-2-XPh)NiBr] (X = S (1a), PPh (1b)) and palladium(II) complexes [(C6H4CH═NPh-2-XPh)PdCl] (X = S (2a), PPh (2b)) were synthesized from the reactions of La and Lb (La = BrC6H4CH═NPh-2-SPh, Lb = BrC6H4CH═NPh-2-PPh2) with (DME)NiBr2 and (COD)PdCl2, respectively, in good yields. All complexes were fully characterized by IR, NMR, and elemental analyses. Single-crystal X-ray diffraction analysis of complex 2a revealed an almost square-planar geometry of the metal center. After activation with methylaluminoxane (MAO), the title complexes 1a,b and 2a,b can be used as catalysts for norbornene polymerization to produce vinyl addition type polynorbornene (PNB) with good catalytic activities. The good catalytic activities of complexes 1b and 2b as procatalysts which contain a P atom as the third coordinated atom can be maintained even at high temperature, demonstrating their excellent thermal stability.

Fluoride adducts of niobium(V): Activation reactions and alkene polymerizations

Fluoride coordination derivatives of niobium(V) were tested for their activation capabilities with respect to acetone and to olefins. Activation of acetone (formation of mesityloxide) was observed with NbF4(OMe). Several fluoride coordination derivatives of niobium(V) of different nature (neutral or ionic) and nuclearity, i.e. NbF5L [L=Et2O, 4, thf, 5 (thf is tetrahydrofuran), MeOH, 6, EtOH, 7], (NbF4L2)(NbF6) [L=dmf, 8 (dmf is dimethylformamide), dme, 9 (dme is dimethoxyethane)], (NbF4L4)(NbF6) [L=thf, 10, Et2O, 11, MeCN, 12], [S(NMe)3][NbF6], 13, NbF4OMe, 1, NbF4OPh, 3), NbF3(OPh)2, 14, NbF2(OPh)3, 15 and NbF2(OEt)3, 16, promoted the polymerization of ethylene using AlMe3-depleted methylaluminoxane as cocatalyst. Highly linear polyethylene was obtained. Compound 3, upon activation with methylaluminoxane, promoted ring-opening metathesis polymerization (ROMP) of norbornene, affording polymers with a slight excess of trans content.

Synthesis, structure, and catalytic activity of nickel complexes with new chiral binaphthyl-based NHC-ligands

Two new chiral NHC-nickel complexes have been prepared from the reactions between Ni(OAc)2, K2CO3 or K2CO3/NaBPh4, and imidazolium salts 3 or 4, which are derived from (R)-2,2′-diamino-1,1′-binaphthyl. Treatment of mono-imidazolium salt 3 with 1 equiv of Ni(OAc)2 in the presence of K2CO3 in 1,4-dioxane at 105 °C gives, after recrystallization from a CH2Cl2 solution, the chiral bis-ligated nickel complex (3)2Ni (5). Under similar reaction conditions, bis-imidazolium salt 4 affords a tetranuclear nickel complex [{(4)Ni}3Ni](BPh4)2 (6). All compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 3, 5, 6 have been further confirmed by X-ray diffraction analyses. Nickel complexes 5 and 6 show a good (106 g/mol h) norbornene polymerization activity upon activation with methylaluminoxane (MAO), leading to thermally very stable polynorbornenes.

One-pot synthesis of poly(norbornene)-block-poly(lactide) copolymers using a bifunctional initiator

Block copolymers of poly(norbornene) and poly(lactide) were synthesized in one-pot using a bifunctional initiator bearing a ruthenium complex for the Ring-Opening Metathesis Polymerization (ROMP) of norbornenes and an alcohol to initiate the 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed Ring-Opening Polymerization (ROP) of L-lactide.

Direct synthesis of cis-dihalido-bis(NHC) complex of nickel(ii) and catalytic application in olefin addition polymerization: Effect of halogen co-ligands and density functional theory study

Two novel amine-containing N-heterocyclic carbene ligand precursors [H(1a-b)]Br have been prepared in good yield and fully characterized. Direct syntheses of cis- and trans-dihalido-bis(NHC) nickel complexes [Ni(NHC)2X2] (X = Cl, Br) are reported. The solid structures of trans-[Ni(1a-b)2Br2] (2a-b) and cis-[Ni(1a)2Cl2] (3) were determined by single-crystal X-ray analysis and 3 was found to be the first example of cis-configuration coordination of monodentate NHC ligands to a metal center for dihalido-bis(NHC) nickel complexes. DFT calculations were conducted to determine the energy difference between cis- and trans-isomers of complexes 2a and 3 bearing bromide and chloride co-ligands. The cis-[Ni(1a)2Cl2] (cis-3) is 1.77-1.55 kcal mol(-1) lower in energy than its trans-isomer in polar solvents including CH2Cl2 and THF, while the trans-[Ni(1a)2Br2] (trans-2a) is more stable than the cis-isomer similarly in the gas phase. The cis nickel complex 3 with two coordinated monodentate NHCs was tested for olefin addition polymerization at standard conditions. It was found that cis-3 was inactive in ethylene polymerization but showed moderate catalytic activities (0.5-3.0 × 10(6) g of PNB (mol of Ni)(-1) h(-1)) in the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst.

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.

Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3

In this study, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3 (1, (W 3 W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE–COOH), OH (NBE–OH), CN (NBE–CN), COOMe (NBE–COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten–tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal–metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%–86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (–COOH, –OH, –CN) deactivate 1, whereas substrates bearing softer ones (–COOMe, –CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed.