Synthesis and characterization of tridentate [O−N(H)X] titanium complexes and their applications in olefin polymerization

A series of [O^?N(H)X]TiCl₃ complexes derived from (arylamino)methylene phenol are prepared. The molecular structures of the complexes are characterized by ¹H NMR, ¹³C NMR, and X‐ray analysis. Upon activation with modified methylaluminoxane (MMAO), the titanium complexes display high thermal stability and single‐site like ethylene (co)polymerization behavior at the temperatures of up to 150 °C. 1‐Octene and 1‐octadencene prove suitable to be incorporated into polyethylene backbone at 110 °C and the highest activity of 1.89 × 10⁶ g/mol(Ti)·h·atm can be achieved. The pendant group X has great influence on the catalytic behaviors of the complexes, and PPh₂ proves to be the optimal group. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2495–2503     

Copolymerization of ethylene with cycloolefins or cyclodiolefins by a constrained‐geometry catalyst

The copolymerization of ethylene and cycloolefins [cyclopentene (CPE), cyclohexene (CHX), cycloheptene (CHP), cyclooctene (COT), cyclododecene (CDO), norbornene (NB), and 5,6‐dihydrodicyclopentadiene HDCPD] and cyclodiolefins [1,3‐cyclopentadiene (CPD), 1,4‐cyclohexadiene (CHD), 1,5‐cyclooctadiene (COD), 2,5‐norbornadiene (NBD), and dicyclopentadiene (DCPD)] was investigated with a constrained‐geometry catalyst, dimethylsilylene(tetramethylcyclopentadienyl)(N‐tert‐butyl)titanium dichloride, with methyl isobutyl aluminoxane as a cocatalyst. In the copolymerization with cycloolefins, the olefins, except for CHX, CDO, and HDCPD, were copolymerized via the 1,2‐insertion mode with the following reactivity: NB > CHP > COT > CPE. In the copolymerization with cyclodiolefins, corresponding copolymers, except for copolymerization with CHD, were obtained. A crosslinking fraction was detected in the copolymers with COD and NBD. The reactivity of the cyclodiolefins, except for COD, was higher than that of the cycloolefins. CPD was copolymerized via 1,2‐insertion, 1,4‐insertion or 1,2‐insertion of dimerized DCPD. The copolymerization with COD showed peculiar behavior under the copolymerization condition of a high COD concentration in the feed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1285–1291, 2005     

Appreciable norbornene incorporation in the copolymerization of ethylene/norbornene using titanium catalysts containing trianionic N[CH2CH(Ph)O]33− ligands

The newly synthesized 1‐TiCl (C₃ symmetric) and 2‐TiCl (C_s symmetric) precatalysts in combination with MAO polymerized ethylene, cyclic olefins, and copolymerized ethylene/norbornene in good yields. The catalyst with C₃ symmetry exhibits moderate catalytic activity and efficient norbornene incorporation for E/NBE copolymerization in the presence of MAO [activity = 360 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL, 10 min], affording poly(ethylene‐co‐NBE)s with high norbornene contents (42.0%) and the C_s symmetric catalyst showed an activity of 420 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL affording poly(ethylene‐co‐NBE)s with 33.0% norbornene content. The effect of monomer concentration at ambient temperature and constant Al/Ti ratio for the homo and copolymerization was studied in a detailed manner. We found that apart from the electronic environment around the metal center the steric environment provided by the symmetry of the catalyst systems has a considerable influence on the percentage of norbornene content of the copolymer obtained. We also found that with a given catalyst a variable clearly influencing the copolymer microstructure, hence also the copolymer properties, is the monomer concentration at a given feed ratio. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 444–452, 2008     

Copolymerization of ethylene with isoprene promoted by titanium complexes containing a tetradentate [OSSO]‐type bis(phenolato) ligand

Copolymerization of ethylene with isoprene (IP) catalyzed by 1,4‐dithabutanediyl‐linked bis(phenolato) titanium complexes 1 and 2 and methylaluminoxane (MAO) produced exclusively ethylene‐IP copolymers with good activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with IP content ～60%. The copolymer microstructure was fully elucidated by ¹³C‐NMR spectroscopy of the copolymers with various IP content revealing a strong tendency to the alternating microstructure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4200–4206, 2010     

Ethylene homopolymerizaton and copolymerizaton by vanadium(III) complexes containing tridentate or tetradentate iminopyrrolyl ligands

Iminopyrrolyl vanadium(III) complexes 2a–b bearing tridentate ligands [C₄H₃NCH?NC₆H₄L]VCl₂(THF) [L = 2‐P(C₆H₅)₂ ( 2a ), 2‐SMe ( 2b )] and complexes 2c–d with tetradentate ligands [(C₄H₃NCH?N)₂R]VCl(THF) [R = 1,2‐C₆H₄ ( 2c ), 1,2‐C₂H₄ ( 2d )] have been synthesized in high yields. With diethylaluminium chloride as a cocatalyst, complexes 2a–d were investigated as efficient catalysts for ethylene polymerization under various reaction conditions, and exhibited high catalytic activity and remarkable thermal stability. With these complexes, high molecular weight polymers with unimodal molecular weight distributions were obtained, indicating that the polymerization reaction took place in a single‐site nature. Ethylene/1‐hexene copolymerizations were also investigated in the presence of Et₂AlCl. Both increasing ligand denticity and introducing softer atom into the sidearm of the ligands significantly influenced catalytic activity, comonomer incorporation, and the molecular weights of the resultant polymers, suggesting that both the steric and the electronic effects of the ligands played an important role in adjusting chain propagation and transfer rate. The chain transfer mechanisms involved in the copolymerization process were investigated by carefully analyzing the microstructure of the copolymers. The signals of vinyl, disubstituted and tri‐substituted vinylene double bond end groups were detected in the copolymer obtained by 2a /Et₂AlCl system but not in those by 2b–c /Et₂AlCl systems, indicating that bulky electron‐donating group, ? P(C₆H₅)₂, may lead to those unusual transfer reactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Copolymerization of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes

The copolymerizations of ethylene and cyclopentene with bis(β‐enaminoketonato) titanium complexes {[(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂; R₁ = CF₃ and R₂ = CH₃ for 1a , R₁ = Ph and R₂ = CF₃ for 1b ; and R₁ = t‐Bu and R₂ = CF₃ for 1c } activated with modified methylaluminoxane (MMAO) as a cocatalyst were investigated. High‐molecular‐weight copolymers with cis‐1,2‐cyclopentene units were obtained. The catalyst activity, cyclopentene incorporation, polymer molecular weight, and polydispersity could be controlled over a wide range through the variation of the catalyst structure and reaction parameters, such as the Al/Ti molar ratio, cyclopentene feed concentration, and polymerization reaction temperature. The complex 1b /MMAO catalyst system exhibited the characteristics of a quasi‐living ethylene polymerization and an ethylene–cyclopentene copolymerization and allowed the synthesis of polyethylene‐block‐poly(ethylene‐co‐cyclopentene) diblock copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1681–1689, 2005     

Ethylene polymerization and ethylene/hexene copolymerization by vanadium(III) complexes bearing bidentate phenoxy‐phosphine oxide ligands

A series of novel vanadium(III) complexes bearing bidentate phenoxy‐phosphine oxide [O,P=O] ligands, (2‐R₁‐4‐R₂‐6‐Ph₂P=O‐C₆H₂O)VCl₂(THF)₂ ( 2a : R₁ = R₂ = H; 2b : R₁ = F, R₂ = H; 2c : R₁ = tBu, R₂ = H; 2d : R₁ = Ph, R₂ = H; 2e : R₁ = R₂ = Me; 2f : R₁ = R₂ = tBu; 2g : R₁ = R₂ = CMe₂Ph) have been synthesized by adding 1 equiv of the ligand to VCl₃(THF)₃ dropwise in the presence of excess triethylamine. Under the same conditions, the adding of VCl₃(THF)₃ to 2.0 equiv of the ligand afforded vanadium(III) complexes bearing two [O,P=O] ligands ( 3c , 3f ). All the complexes were characterized by FTIR and mass spectra as well as elemental analysis. Structures of complexes 2c and 3c were further confirmed by X‐ray crystallographic analysis. On activation with Et₂AlCl and ethyl trichloroacetate, these complexes displayed high catalytic activities for ethylene polymerization (up to 26.4 kg PE/mmol_V·h·bar) even at high reaction temperature (70 °C) indicative of high thermal stability, and produced high molecular weight polymers with unimodal molecular weight distributions. Additionally, the complexes with optimized structure exhibited high catalytic activities for ethylene/1‐hexene copolymerization. Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled in a wide range via the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and reaction temperature. The monomer reactivity ratios r_E and r_H were determined according to ¹³C NMR spectra, which indicated these complexes preferred ethylene to 1‐hexene in the copolymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5298–5306     

Olefin polymerization and copolymerization by complexes bearing [ONNO]‐Type salan ligands: Effect of ligand structure and metal type (titanium,zirconium, and vanadium)

A series of novel titanium(IV) complexes bearing tetradentate [ONNO] salan type ligands: [Ti{2,2′‐(OC₆H₃‐5‐t‐Bu)₂‐NHRNH}Cl₂] (Lig¹TiCl₂: R = C₂H₄; Lig²TiCl₂: R = C₄H₈; Lig³TiCl₂: R = C₆H₁₂) and [Ti{2,2′‐(OC₆H₂‐3,5‐di‐t‐Bu)₂‐NHC₆H₁₂NH}Cl₂] (Lig⁴TiCl₂) were synthesized and used in the (co)polymerization of olefins. Vanadium and zirconium complexes: [ M{2,2′‐(OC₆H₃‐3,5‐di‐t‐Bu)₂‐NHC₆H₁₂NH}Cl₂] (Lig⁴VCl₂: M = V; Lig⁴ZrCl₂: M = Zr) were also synthesized for comparative investigations. All the complexes turned out active in 1‐octene polymerization after activation by MAO and/or Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄]. The catalytic performance of titanium complexes was strictly dependent on their structures and it improves for the increasing length of the aliphatic linkage between nitrogen atoms (Lig¹TiCl₂ << Lig²TiCl₂ < Lig³TiCl₂) and declines after adding additional tert‐Bu group on the aromatic rings (Lig³TiCl₂ < Lig⁴TiCl₂). The activity of all titanium complexes in ethylene polymerization was moderate and the properties of polyethylene was dependent on the ligand structure, cocatalyst type, and reaction conditions. The Et₂AlCl‐activated complexes gave polymers with lover molecular weights and bimodal distribution, whereas ultra‐high molecular weight PE (up to 3588 kg mol^?1) and narrow MWD was formed for MAO as a cocatalyst. Vanadium complex yielded PE with the highest productivity (1925.3 kg mol_v^?1), with high molecular weight (1986 kg mol^?1) and with very narrow molecular weight distribution (1.5). Copolymerization tests showed that titanium complexes yielded ethylene/1‐octene copolymers, whereas vanadium catalysts produced product mixtures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2111–2123     

Efficient ethylene/norbornene copolymerization by half‐titanocenes containing imidazolin‐2‐iminato ligands and MAO catalyst systems

Ethylene copolymerizations with norbornene (NBE) using half‐titanocenes containing imidazolin‐2‐iminato ligands, Cp′TiCl₂[1,3‐R₂(CHN)₂C?N] [Cp′ = Cp ( 1 ), ^tBuC₅H₄ ( 2 ); R = ^tBu ( a ), 2,6‐ⁱPr₂C₆H₃ ( b )], have been explored in the presence of methylaluminoxane (MAO) cocatalyst. Complex 1a exhibited remarkable catalytic activity with better NBE incorporation, affording high‐molecular‐weight copolymers with uniform molecular weight distributions, whereas the tert‐BuC₅H₄ analog ( 2a ) showed low activity, and the resultant polymer prepared by the Cp‐2,6‐diisopropylphenyl analog ( 1b ) possessed broad molecular weight distribution. The microstructure analysis of the poly(ethylene‐co‐NBE)s prepared by 1a suggests the formation of random copolymers including two and three NBE repeating units. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2575–2580     

Ethylene polymerization by the chromium catalysts based on bidentate [O,PO] or [S,P] ligands

Novel chromium catalysts based on bidentate phenoxy‐phosphinoyl (HO‐2R₁‐4R₂‐6(Ph₂P?O)C₆H₂: R₁ = R₂ = H, 3a ; R₁ = tBu, R₂ = H, 3b ; R₁ = R₂ = tBu, 3c ; R₁ = R₂ = cumyl, 3d ; R₁ = anthracenyl, R₂ = H, 3e ) and thiophenol‐phosphine (HS‐2R₁‐4R₂‐6(Ph₂P)C₆H₂: R₁ = R₂ = H, 4a ; R₁ = SiMe₃, R₂ = H, 4b ) were prepared and characterized. Treatment with modified methyaluminoxane, these catalysts displayed moderate to high‐catalytic activities for ethylene polymerization. The activities of them were higher than those of the corresponding catalysts based on bidentate phenoxy‐phosphine ligands. Both the coordinated donors and the ortho‐substituent of the ligands played an important role in improving catalytic activity. The effects of reaction parameters, such as cocatalyst and Al/Cr molar ratio as well as reaction temperature, on ethylene polymerization behaviors were investigated in detail for two favorable catalytic systems, 3b /CrCl₃(thf)₃ and 4b /CrCl₃(thf)₃. Catalyst 4b /CrCl₃(thf)₃ displayed higher catalytic activity and better temperature tolerance for ethylene polymerization than 3b /CrCl₃(thf)₃. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 311–319, 2010     

Copolymerization of carbon dioxide and cyclohexene oxide catalyzed by chromium complexes bearing semirigid [ONSO]‐type ligands

Chromium complexes supported by tetradentate dianionic imine‐thioether‐bridged bis(phenol) ligands were prepared and employed in the synthesis of poly(cyclohexene carbonate) via the copolymerization of CO₂ and cyclohexene oxide. The catalytic activity, product selectivity, and kinetic behaviors of these [ONSO]Cr^III complexes have been systematically investigated. Results indicate the presence of electron‐withdrawing substituents on the ligands to enhance catalytic activity and polymer selectivity. A turnover frequency of 100 h^?1 is observed at a temperature of 110 °C, producing polycarbonate with >60% selectivity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1938–1944     

Synthesis and characterization of titanium complexes bearing sulfoxide groups and their catalytic behaviors in ethylene homo- and copolymerization

<正>1 Experimental section 1.1 General information All manipulations of air- and/or moisture-sensitive compounds were performed under nitrogen atmosphere using standard Schlenk techniques. 1H NMR and 13 C NMR spectra were recorded on a Varian XL-300 MHz spectrometer with TMS as the internal standard. Mass spectra were obtained using a HP5959 A spectrometer. IR spectra were recorded using a Nicolet AV-360 spectrometer. Elemental analysis was performed by the Analytical Laboratory of Shanghai Institute of Organic Chemistry(CAS). Mn, Mw, and Mw/Mn values of polymers were determined with a Waters Alliance GPC 2000 series at     

Copolymerization behavior of titanium imidazolin‐2‐iminato complexes

Monocyclopentadienyl titanium imidazolin‐2‐iminato complexes [Cp′Ti(L)X₂] 1a (Cp′ = cyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), 1b (X = CH₃); 2 (Cp′ = cyclopentadienyl, L = 1,3‐diisopropylimidazolin‐2‐imide, X = Cl); 3 (Cp′ = tert‐butylcyclopentadienyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide, X = Cl), upon activation with methylaluminoxane (MAO) were active for the polymerization of ethylene and propylene and the copolymerization of ethylene and 1‐hexene. Catalysts derived from imidazolin‐2‐iminato tropidinyl titanium complex 4 = [(Trop)Ti(L)Cl₂] (Trop = tropidinyl, L = 1,3‐di‐tert‐butylimidazolin‐2‐imide) were much less active. Narrow polydispersities were observed for ethylene and propylene polymerization, but the copolymerization of ethylene/hexene led to bimodal molecular weight distributions. The productivity of catalysts derived from the dialkyl complex 1b activated with [Ph₃C][B(C₆F₅)₄] or B(C₆F₅)₃ were less active for ethylene/hexene copolymerization but yielded ethylene/hexene copolymers of narrower molecular weight distributions than those derived from 1a/MAO. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6064–6070, 2008     

Copolymerization of carbon dioxide with cyclohexene oxide catalyzed by bimetallic dysprosium complexes containing hydrazine‐functionalized Schiff‐base derivatives

A series of dinuclear Dy^III acetate complexes containing three different hydrazine‐functionalized Schiff‐base ligands ( hmb , hmi, and hb ) have been synthesized by one‐pot reaction with Dy(OAc)₃·4H₂O as the metal precursor. [Dy₂( hmb )₂(OAc)₄]·MeCN ( 1 ·MeCN) and [Dy₂( hmi )₂(OAc)₂(MeOH)₂]·H₂O ( 2 ·H₂O) with keto and enol forms of the corresponding ligands, respectively, were shown the similar core structures but different ratio of Dy^III to OAc^–. Moreover, the different coordination environments of complex [Dy₂( hb )₂(μ‐OAc)₂(OAc)₂(H₂O)₂]·DMF·H₂O ( 3 ·DMF·H₂O) also offered an opportunity to understand the relationship between structural model and catalytic properties. Bimetallic dysprosium complexes 1 – 3 were demonstrated to be active catalysts for copolymerization of carbon dioxide (CO₂) and cyclohexene oxide (CHO) without cocatalysts. To the best of our knowledge, well‐defined catalyst 2 appears to be the first example of an air‐stable bimetallic dysprosium complex that is effective for CO₂/CHO copolymerization and the formation of the perfectly alternating poly(cyclohexenecarbonate) with a high molecular weight. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 321–328     

Alternating Ring-Opening Metathesis Copolymerization of Norborn-2-ene with cis-Cyclooctene and Cyclopentene

Ru-alkylidenes based on unsymmetrical imidazolin-2-ylidenes, were used for the alternating copolymerization of norborn-2-ene (NBE) with cis-cyclooctene (COE) and cyclopentene (CPE), respectively. Alternating copolymers, i.e., poly(NBE-alt-COE)_n and poly(NBE-alt-CPE)_n containing up to 97 and 91% alternating diads, respectively, were obtained. The copolymerization parameters of the alternating copolymerization of NBE with CPE under the action of different initiators were determined using a first order Markov model. Hydrogenation of poly(NBE-alt-COE)_n yielded a fully saturated, hydrocarbon-based polymer.     

Copolymerization of carbon monoxide with 1,3-cyclopentadiene by palladium complexes

Copolymerization of carbon monoxide with 1,3-cyclopentadiene (CPD) by palladium complexes, [Pd(CH₃CN)_4?n (PPh₃)n] (BF₄)₂, n = 1–3 (especially n = 1), was studied at 60°C. Results of elementary analysis, infrared spectra, and NMR spectra showed that copolymers containing ketone and ring structures were produced. Phosphorus compounds such as PPh₃ were found to be more effective stabilizing ligands for the catalytic activity compared to arsenic or nitric ligands. A higher activity of the catalyst for the copolymerization of CPD with carbon monoxide was observed in noncoordinating solvents such as CHCl₃ even at a pressure as low as 300 psi. The amount of 1,2 structure for the CPD-CO copolymer increased as the polarity of solvent increased. The copolymer was confirmed to be partially crystalline by the x-ray diffraction. TGA shows that weight loss of copolymer starts at 120°C and the maximum peak of decomposition occurs at 469°C. © 1993 John Wiley & Sons, Inc.     

Ethylene polymerizations,and the copolymerizations of ethylene with hexene or norbornene with highly active mono(β‐enaminoketonato) vanadium(III) catalysts

Five novel vanadium(III) complexes [PhN = C(R₂)CHC(R₁)O]VCl₂(THF)₂ ( 4a : R₁ = Ph, R₂ = CF₃; 4b : R₁ = t‐Bu, R₂ = CF₃; 4c : R₁ = CF₃, R₂ = CH₃; 4d : R₁ = Ph, R₂ = CH₃; 4e : R₁ = Ph, R₂ = H) have been synthesized and characterized. On activation with Et₂AlCl, all the complexes, in the presence of ethyl trichloroacetate (ETA) as a promoter, are highly active precatalysts for ethylene polymerization, and produce high molecular weight and linear polymers. Catalyst activities more than 16.8 kg PE/mmol_V h bar and weight‐average molecular weights higher than 173 kg/mol were observed under mild conditions. The copolymerizations of ethylene and norbornene or 1‐hexene with the precatalysts were also explored, which leads to high molecular weight copolymers with high comonomer incorporation. Catalyst activity, comonomer incorporation, and polymer molecular weight as well as polydispersity index can be controlled over a wide range by the variation of precatalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and polymerization temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2038–2048, 2008     

Copolymerization of ethylene with acrylonitrile promoted by novel nonmetallocene catalysts with phenoxy‐imine ligands

A series of novel nonmetallocene catalysts with phenoxy‐imine ligands was synthesized by the treatment of phthaldialdehyde, substituted phenol with TiCl₄, ZrCl₄, and YCl₃ in THF. The structures and properties of the catalysts were characterized by ¹H NMR and elemental analysis. These catalysts were used for copolymerization of ethylene with acrylonitrile after activated by methylaluminoxane (MAO). The effects of copolymerization temperature, Al/M (M = Ti, Zr, and Y) ratio in mole, concentrations of catalyst and comonomer on the polymerization behaviors were investigated in detail. These results revealed that these catalysts were favorable for copolymerization of ethylene with acrylonitrile. Cat. 3 was the most favorable one for the copolymerization of ethylene with acrylonitrile, and the catalytic activity was up to 2.19 × 10⁴ g PE/mol.Ti.h under the conditions: polymerization temperature of 50 °C, Al/Ti molar ratio of 300, catalyst concentration of 1.0 × 10^–4 mol/L, and toluene as solvent. The resultant polymer was characterized by FTIR, cross‐polarization magic angle spinning, ¹³C NMR, WAXD, GPC, and DSC. The results confirmed that the obtained copolymer featured high‐weight–average molecular weight, narrow molecular weight distribution about 1.61–1.95, and high‐acrylonitrile incorporation up to 2.29 mol %. Melting temperature of the copolymer depended on the content of acrylonitrile incorporation within the copolymer chain. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012