Polymerization of norbornene using bis(β‐ketoamino)nickel(II)/MAO catalytic systems

The polymerizations of norbornene were investigated using a series of bis(β‐ketoamino)nickel(II) complexes( 1–6 ) in combination with methylaluminoxane (MAO) in toluene solution. The effects of catalyst structure, Al/Ni molar ratio, reaction temperature, and reaction time on catalytic activity and molecular weight of the polynorbornene were examined in detail. The electronic effect of the substituent around the imino group in the ligand is stronger than the steric bulk one on the polymerization activities, and the activities are in the order of 1 > 2 > 4 > 5 > 6 > 3 . The obtained polynorbornenes were characterized by means of ¹H‐NMR, ¹³C‐NMR, FTIR, TG, and WAXD techniques. The analyses results of polymers' structures and properties indicate that the polymerization reaction of norbornene runs in vinyl‐addition polymerization mode. The obtained polynorbornene was confirmed to be vinyl‐type and atactic polymers and showed good thermostability (T_dec > 458°C) and were noncrystalline but had short‐range order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4172–4180, 2006     

Synthesis and characterization of tridentate phenoxy‐imine ligand [N,N,O] nickel(II) and palladium(II) complexes and their catalytic behaviors in vinyl polymerization of norbornene

In this study, new complexes LNiCl( 1 ), LNiBr( 2 ), LNiI( 3 ), and LPdCl( 4 ) (L = 4,6‐di‐tert‐butyl‐2‐(N‐(quinolin‐8‐yl)iminomethyl)phenolato) have been synthesized and characterized. X‐ray diffraction studies on Complexes 1 and 4 revealed that N, N, O, and halogen atoms coordinated to metal, with a nearly square planar geometries in all cases. All these complexes are robust and exhibit high activities for the addition polymerization of norbornene (NB) with methylaluminoxane as cocatalyst [up to 47.62 kg PNB(mmol of Ni)^?1h^?1] and also lead to various activities and molecular weights of polynorbornenes under different reaction conditions. It is noteworthy that Complexes 1 and 4 show better activity under higher reaction temperature of 80°C. However, Complex 2 showed lower activity, and Complex 3 was found nearly inert toward NB polymerization, probably, because of thermal instability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of tris(pentafluorophenyl)borane on the activation of zerovalent-nickel complex in the addition polymerization of norbornene

The effects of B(C₆F₅)₃ on the activation of the Ni(0) and Ni(II) complexes were studied in the polymerization of norbornene. The Ni(0) complex, such as bis(1,5-cyclooctadiene)nickel (Ni(COD)₂ (1), biacetylbis(2,6-diisopropylphenylimmine)(1,3-butadiene)nickel (2), or tetrakis(triphenylphosphine)nickel (5), in combination with B(C₆F₅)₃, was determined to have high activity in the polymerization of norbornene. On the other hand, the Ni(II) complex with B(C₆F₅)₃ did not provide any activity at all under analogous conditions regardless of the structure of the Ni(II) complex. The use of other borane compounds, such as B(C₆H₅)₃, BEt₃, and BF₃ etherate, with Ni(COD)₂ (1) in place of B(C₆F₅)₃ clearly showed the main functions of B(C₆F₅)₃. The high Lewis acidity of B(C₆F₅)₃ enabled it to activate catalytic complexes, thus inducing polymerization. The study of the ¹H, ¹³C, and ¹⁹F NMR spectra of the polynorbornene produced with Ni(COD)₂ (1) and B(C₆F₅)₃, in the presence or absence of ethylene, showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the Ni-C bond of the C₆F₅ ligand. A new polymerization mechanism was proposed in norbornene polymerization, wherein the active complex formed from Ni(COD)₂ (1) and B(C₆F₅)₃ acts as a catalyst.     

Vinyl polymerization of norbornene over supported nickel catalyst

A series of nickel complexes, bis(salicylideneiminato)nickel(II), were supported on spherical MgCl₂ and SiO₂. Scanning electron microscopy, energy‐dispersed X‐ray spectroscopy, and the BET method for surface areas measurements were utilized to examine the supporting process of the catalysts. The particle morphology of the original support is retained and replicated throughout the supported catalyst preparation and norbornene polymerization. Spherical polymer particle morphology was achieved, without reactor fouling. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2233–2240, 2006     

Vinyl polymerization of norbornene with bispyrazolylimine dinickel(II)/methylaluminoxane catalytic system

The polymerization of norbornene has been investigated in the presence of two novel bispyrazolylimine dinickel(II) complexes bis-2-(C₃HN₂Me₂-3,5)(C(Ph) = N(4-RC₆H₄)Ni₂Br₄ (complex 1, R = H; complex 2, R = OCH₃) activated by methylaluminoxane. The two catalytic systems show high activity (up to 1.83 × 10⁶ gPNBE/(molNi·h)) for norbornene polymerization and provide polynorbornene (PNBE) with higher molecular weights (M _w = 4.44 × 10⁵–11.57 × 10⁵ g/mol) and narrower molecular weight distributions about 2.0. The electron-donating of methoxyl group in complex 2 could enhance the catalytic activity for norbornene polymerization, however, the molecular weights of polymers were decreased. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time and catalyst concentration on catalytic activity, and molecular weight of the PNBEs were investigated in detail. The obtained PNBEs were characterized by means of ¹H NMR, FTIR, and thermogravimetric analyses. The analyses results of PNBE indicated that the norbornene polymerization is vinyl-type polymerization rather than ring-opening metathesis polymerization.     

Influence of imine‐carbon substituent in 6‐bromo‐2‐iminopyridine‐based cobalt(II) complexes on 1,3‐butadiene polymerization

6‐Bromo‐2‐iminopyridine cobalt(II) complexes bearing different imine‐carbon substituents ( Co1 – Co7 ) were synthesized and subsequently employed for 1,3‐butadiene polymerization. All the complexes were identified using Fourier transform infrared spectra and elemental analysis, and complexes Co1 and Co3 were further characterized using single‐crystal X‐ray diffraction analysis, demonstrating they adopted distorted trigonal bipyramidal and tetrahedral geometries, respectively. Activated by methylaluminoxane, these complexes exhibited high cis‐1,4 selectivity, and the activity was highly dependent on the substituent at the imine‐carbon position of the ligand. Addition of PPh₃ to the polymerization systems could enhance the catalytic activity and simultaneously switched the selectivity from cis‐1,4 to cis‐1,2 manner. On the basis of the obtained results, a plausible mechanism involving the regulation of selectivity and activity is proposed. © 2019 Society of Chemical Industry     

Copolymerization of ethylene/5‐ethylidene‐2‐norbornene with bis (2‐phenylindenyl) zirconium dichloride catalyst: I. Optimization of the operating conditions by response surface methodology

In this study, the copolymerization of ethylene with nonconjugated diene (5‐ethylidene‐2‐norbornene) was carried out with a bis(2‐PhInd) ZrCl₂ metallocene catalyst. Some polymerization factors that were considered affective on the catalyst activity, including comonomer content in the feed, ethylene pressure, and polymerization temperature, were investigated via response surface methodology to determine the optimum polymerization conditions. We found that the comonomer content in the feedstock had no enormous effect on the catalyst activity depression. Also, the polymerization temperature increment through the scrutinized range decreased the copolymerization activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nickel(II) complexes bearing the bis(β‐ketoamino) ligand for the copolymerization of norbornene with a higher 1‐alkene

A novel bis(β‐ketoamino)Ni(II) complex catalyst, Ni{CF₃C(O)CHC[N(naphthyl)]CH₃}₂, was synthesized, and the structure was solved by a single‐crystal X‐ray refraction technique. The copolymerization of norbornene with higher 1‐alkene was carried out in toluene with catalytic systems based on nickel(II) complexes, Ni{RC(O)CHC[N(naphthyl)]CH₃}₂(R?CH₃, CF₃) and B(C₆F₅)₃, and high activity was exhibited by both catalytic systems. The effects of the catalyst structure and comonomer feed content on the polymerization activity and the incorporation rates were investigated. The reactivity ratios were determined to be r_1‐octene = 0.009 and r_norbornene = 13.461 by the Kelen–Tüdõs method for the Ni{CH₃C(O)CHC[N(naphthyl)]CH₃}₂/B(C₆F₅)₃ system. The achieved copolymers were confirmed to be vinyl‐addition copolymers through the analysis of ¹H‐NMR and ¹³C‐NMR. The thermogravimetric analysis results showed that the copolymers exhibited good thermal stability (decomposition temperature, T_dec > 400°C), and the glass‐transition temperature of the copolymers were observed between 215 and 275°C. The copolymers were confirmed to be noncrystalline by wide‐angle X‐ray diffraction analysis and showed good solubility in common organic solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Copolymerization of norbornene and <Emphasis Type="Italic">n</Emphasis>-butyl methacrylate catalyzed by bis-(β-ketoamino)nickel(II)/B(C<Subscript>6</Subscript>F<Subscript>5</Subscript>)<Subscript>3</Subscript> catalytic system

Abstract  

Copolymerization of norbornene with n-butyl methacrylate (n-BMA) was carried out with catalytic systems of bis-(β-ketoamino)nickel(II) complexes Ni{RC(O)CHC[N(naphthyl)]CH₃}₂ (R = CH₃, CF₃) and B(C₆F₅)₃ in toluene and exhibited high activity for both catalytic systems. Influence of the catalyst structure and comonomer feed content on the polymerization activity as well as on the incorporation rates were investigated. The catalysis was proposed to involve the insertion mechanism of norbornene and n-BMA catalyzed by bis-(β-ketoamino)nickel(II)/B(C₆F₅)₃ catalytic systems, and the decreasing polymerization activity with an increasing content of n-BMA in the feedstock composition could be attributed to the competition of carbonyl group coordination onto the Ni(II) active center instead of the olefin double bond. The reactivity ratios were determined to be r _n-BMA = 0.095 and r _norbornene = 12.626 by the Kelen–Tüd?s method. The copolymer films prepared show good transparency in the visible region.     

Copolymerization of Norbornene and Styrene Catalyzed by a Series of Bis(β-ketoamine) Nickel(II) Complexes in the Presence of Methylaluminoxane

Summary Random copolymerization of norbornene with styrene was studied by using a series of late metal catalysts/MAO. The precatalysts used here are nickel complexes with b-ketoamine ligands based on pyrazolone derivatives. The copolymers obtained here suggest that only one type of active species is present. Copolymers were characterized by ¹³C NMR, Gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and FT-IR spectra. The analyses of the product by ¹H NMR and ¹³C NMR spectra gave the verification of “true” random vinyl addition copolymer. Varying the monomer feed ratio controlled the composition of the copolymers. A copolymerization reactivity ratio (r_NBE = 20.35 and r_Sty = 0.027) indicates a much higher reactivity of norbornene, which suggests a coordination polymerization mechanism. The solubility and processability of the copolymers are improved relative to polynorbornene and the thermostability of the copolymers is improved relative to polystyrene.     

Fe(acac)n and Co(acac)n bearing different bis(imino)pyridine ligands for ethylene polymerization and oligomerization

A series of iron and cobalt complexes ligated with different bis(imino)pyridyl ligands were synthesized and used in ethylene polymerization. The reaction temperature and Al/Fe ratio had a great influence on the activities and properties of the polymer in the iron system when methylaluminoxane was used as the cocatalyst. Bimodal polyethylene, unimodal polyethylene, and oligomers were achieved with ethylene polymerization according to the structures of the ligands and polymerization conditions. The cobalt systems showed low activities when bis(imino)pyridyl was used as the ligand in comparison with the iron system catalysts. Ethylene oligomerization was conducted, and the main products were 1‐butylene and 1‐hexene. A fast deactivation process was observed from the curve of the polymerization kinetics. The polymerization mechanism was examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

双(咪唑啉-2-亚胺)吡啶铁、镍配合物引发的烯烃聚合行为

研究了含双(咪唑啉-2-亚胺)吡啶配体的铁、镍配合物在不同温度、不同助催化剂下对烯烃聚合行为的研究。铁配合物经改性甲基铝氧烷(MMAO)的活化对乙烯聚合具有良好的活性,并于60℃达到最高活性为1.68×10~6g PE/mol/h,且在较高的温度下活性并未衰减,所得聚乙烯的数均分子量可高达22万。镍配合物分别在助催化剂MMAO和甲基铝氧烷(MAO)的作用下对降冰片烯均表现出很高的活性,MAO体系的活性最高达7.65×10~7g/mol/h,产物的数均分子量达到50万;MMAO体系的活性虽然比MAO体系低(1.464×10~7g/mol/h),但产物的数均分子量最高可达150万。     

Vinyl polymerization of norbornene with dinuclear diimine nickel dichloride/MAO

Vinyl‐addition polymerization of norbornene was accomplished by two novel dinuclear diimine nickel dichloride complexes in combination with methylaluminoxane (MAO). The activities were moderate. The catalyst structure, Al/Ni molar ratio, solvents, and polymerization temperature all affected the catalytic activities. The obtained polynorbornenes were characterized by ¹H‐NMR, ¹³C‐NMR, FTIR, DSC, WAXD, and intrinsic viscosity measurements. The vinyl‐addition polymers were amorphous but with a short‐range order and high packing density. The polynorbornenes showed glass transition temperatures (T_g) above 240°C and decomposed above 400°C. The catalyst structure and polymerization conditions have effects on the molecular weight and the microstructure of the polymers. The nickel complex with bulkier substituents in the ligand produced polynorbornene with a higher packing density and higher regularity and, therefore, with higher T_g. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3273–3278, 2003     

Catalytic Behavior of Bis(Pyrrolide-Imine) and Bis(Phenoxy-Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1-Hexene,or Norbornene

This contribution reports the catalytic behavior of bis(pyrrolide-imine)Ti complexes 1 and 2 , [2-(RNCH)-C₄H₃N]₂TiCl₂ ( 1 , R = Ph; 2 , R = cyclohexyl), and bis(phenoxy-imine)Ti complex 3 , [2-(Ph-NCH)-3-t Bu-C₆H₃O]₂TiCl₂ for the copolymerization of ethylene with propylene, 1-hexene, or norbornene. An inspection of the X-ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide-imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy-imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3 . Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1-hexene and incorporated higher amounts of propylene ( 1 ; 30.5 mol%, 2 ; 23.4 mol%) and 1-hexene ( 1 ; 1.9 mol%, 2 ; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1-hexene; 0.4 mol%). The incorporation levels of propylene and 1-hexene displayed by complexes 1 and 2 were lower than those for Cp₂TiCl₂ (propylene; 41.6 mol%, 1-hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents ( 1 ; 32.0 mol%, 2 ; 26.5 mol%) than Cp₂TiCl₂ (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp₂TiCl₂ and provided a copolymer with extremely narrow molecular weight distribution (M_w/M_n 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation.     

Ring‐opening metathesis polymerization of norbornene catalyzed by tantalum and niobium complexes with chelating O‐donor ligands

BACKGROUND: In comparison with group 6 transition metals, such as tungsten and molybdenum, and group 8 metal ruthenium, group 5 metal‐based catalysts for ring‐opening metathesis polymerization (ROMP) have remained much less studied. The few reported ROMP catalysts of group 5 metals require multiple reaction steps to be synthesized, and are highly sensitive to air and moisture. RESULTS: A series of pentavalent tantalum and niobium complexes having catecholato, tropolonato, hinokitiolato, biphenolato and binaphtholato ligands were prepared and their catalytic activities for the ROMP of norbornene (NBE) were studied in the presence of trialkylaluminium as a co‐catalyst. Among these complexes, the tantalum complexes showed high activity upon activation with Buⁱ₃Al. In sharp contrast, the niobium complexes were effectively activated with Me₃Al. The polymers obtained with these complexes had high molecular weights (M_n > 10⁵ g mol⁻¹) and relatively narrow molecular weight distributions (M_w/M_n ≈ 2). CONCLUSION: We found that easily accessible and relatively stable tantalum and niobium complexes with such chelating O‐donor ligands showed high catalytic activity for ROMP of NBE depending on the kind of co‐catalyst. These findings could contribute to future development of ROMP catalysts. Copyright © 2008 Society of Chemical Industry     

Polymerization and characterization of bis(trichlorophenolato)di(pyridine) nickel(II) and bis(tribromophenolato)di(pyridine) nickel(II) dihydrate complexes in solution in the presence of iodine

The syntheses of bis(trihalophenolato)di(pyridine) nickel(II) complexes were achieved in aqueous solution, and their characterizations were performed by Fourier transform infrared (FTIR) spectroscopy, ultraviolet‐visible analysis, differential scanning calorimetry, and elemental analysis. The thermal polymerization of these complexes was studied in toluene solution in the presence of iodine. The effect of time, temperature, and amount of iodine added on the percentage conversion, structure of polymers, and intrinsic viscosity ([η]) were investigated. Polymers were characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopic analyses, glass‐transition temperatures determined by differential thermal analysis, and [η] values determined by the viscometric method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2232–2239, 2002     

Norbornene polymerization and ethylene/norbornene copolymerization catalyzed by constrained geometry cyclopentadienyl-phenoxytitanium catalysts

Norbornene polymerization and ethylene/norbornene copolymerization were studied using constrained geometry complexes 2-(tetramethylcyclopentadienyl)-4,6-di-tert-butylphenoxytitanium dichloride (1), 2-(tetramethylcyclopentadienyl)-6-tert-butylphenoxytitanium dichloride (2), and 2-(tetramethylcyclopentadienyl)-6-phenylphenoxytitanium dichloride (3) as catalysts with AlⁱBu₃ and Ph₃CB(C₆F₅)₄ as cocatalysts. Polymerization results indicate that these catalyst systems are highly active for both the homopolymerization of norbornene and the copolymerization of ethylene with norbornene. The norbornene homopolymerization is vinyl addition polymerization. Ethylene/norbornene copolymers with high norbornene incorporation (>50%) were easily obtained with these catalyst systems by increasing the norbornene feed concentration. The produced polymers were characterized by ¹³C NMR, IR, DSC and GPC.     

Syndiotactic poly(propene-co-norbornene): Synthesis and properties at low norbornene incorporation

Copolymerizations of propene with norbornene were carried out using a syndiotactic metallocene catalyst at low initial comonomer concentrations for different polymerization times. The influence of the norbornene concentration on the catalytic activity and on the resulting material properties has been analyzed. The copolymer molecular weight decreased drastically when small amounts of norbornene were added in reactions which lasted 30 min. When longer reaction times were used the molecular weight increased with time, however living polymerization was ruled out because the polydispersity was ca. 2. The DSC measurements showed copolymers with low crystallinity or which were completely amorphous.     

Novel bis(acetylacetonate)palladium/boron trifluoride etherate catalyst system for the polymerization of norbornene

The boron trifluoride etherate, BF₃OEt₂, was used as an activator towards bis(acetylacetonate)palladium precursor in the polymerization of norbornene. The catalyst system Pd(Acac)₂/BF₃OEt₂ was highly active in the polymerization of norbornene. Catalytic activity up to 20,220 kg/(mol Pd · h) and intrinsic viscosities up to 2.64 dL/g were observed, respectively. Catalytic activity, polymer yield and polymer molecular weight could be controlled by varying the reaction parameters. The molar mass distribution indicates a single-site, highly homogeneous character of the active catalyst species. NMR spectroscopy study of the polymer showed exclusively 2,7-enchained repeating units of polymer backbone.     

Lanthanide(II) amide complexes: Efficient initiators for the living polymerization of methyl methacrylate

Lanthanide(II) complexes supported by amido ligands, [(C₆H₅)(Me₃Si)N]₂Ln(DME)₂ [Ln = Sm ( 1 ) or Yb ( 2 ); DME = 1,2‐dimethoxyethane] and [(C₆H₃? ⁱPr₂‐2,6)(Me₃Si)N]₂Ln(THF)₂ [Ln = Sm ( 3 ) or Yb ( 4 ); THF = tetrahydrofuran], were found to initiate the polymerization of methyl methacrylate (MMA) as efficient single‐component initiators (in toluene for 3 and 4 and in toluene with a small amount of THF for 1 and 2 ) to produce syndiotactic polymers. The catalytic behavior was highly dependent on both the amido ligand and the polymerization temperature. Initiators 3 and 4 initiated MMA polymerization over a wide range of temperatures (20°C to ?40°C), whereas the polymerization with 1 and 2 proceeded smoothly only at low temperatures (≤0°C). The kinetic behavior and some features of the polymerizations of MMA initiated by 3 and 4 were studied at ?40°C. The polymerization rate was first‐order with the monomer concentration. The molar masses of the polymers increased linearly with the increase in the polymer yields, whereas the molar mass distributions remained narrow and unchanged throughout the polymerization; this indicated that these systems had living character. A polymerization mechanism initiated by bimetallic bisenolate formed in situ was proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009