Introduction of reactive functionality by the incorporation of divinylbiphenyl in ethylene copolymerization with styrene or 1‐hexene using aryloxo‐modified half‐titanocenes and MAO catalysts

An efficient introduction of vinyl group into poly (ethylene‐co‐styrene) or poly(ethylene‐co?1‐hexene) has been achieved by the incorporation of 3,3′‐divinylbiphenyl (DVBP) in terpolymerization of ethylene, styrene, or 1‐hexene with DVBP using aryloxo‐modified half‐titanocenes, Cp′TiCl₂(O?2,6‐ⁱPr₂C₆H₃) [Cp′ = Cp*, ^tBuC₅H₄, 1,2,4‐Me₃C₅H₂], in the presence of MAO cocatalyst, affording high‐molecular‐weight polymers with unimodal distributions. Efficient comonomer incorporations have been achieved by these catalysts, and the content of each comonomer could be varied by its initial concentration charged. The postpolymerization of styrene was initiated from the vinyl group remained in the side chain by treatment with n‐BuLi. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2581–2587     

Structure–property transition‐state model for the copolymerization of ethene and 1‐hexene with experimental and theoretical applications to novel disilylene‐bridged zirconocenes

Ethene homopolymerization and copolymerization with 1‐hexene were performed with three new tetramethyldisilylene‐bridged zirconocene catalysts with 2‐indenyl ligand ( A ), 2‐tetrahydroindenyl ligand ( B ), and tetramethyl‐cyclopentadienyl ligand ( C ) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1‐hexene content and a high melting temperature. The reduction in the molecular weight with 1‐hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1‐hexene insertion and a high degree of chain‐end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (Me_nC₅H_5?n)₂ZrCl₂ catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622–1631, 2003     

Pressure and trimethylaluminum effects on ethene/1‐hexene copolymerization with methylaluminoxane‐activated (1,2,4‐Me3Cp)2ZrCl2: Trimethylaluminum suppression of standard termination reactions after 1‐hexene insertion

Ethene homopolymerizations and copolymerizations with 1‐hexene were catalyzed by methylaluminoxane‐activated (1,2,4‐Me₃Cp)₂ZrCl₂. Investigations of the effects of various pressures on the homopolymerizations and copolymerizations and of the effects of different concentrations of trimethylaluminum (TMA) on the copolymerizations were performed. The characteristics of the ethene/1‐hexene copolymers agreed with expectations for changes in the ethene concentration: the incorporation of 1‐hexene decreased, whereas the melting point and crystallinity increased, with increasing pressure. The main termination mechanism of the homopolymerizations was β‐hydrogen transfer to the monomer. Termination mechanisms resulting in vinylidene unsaturations dominated in the copolymerizations. Standard termination mechanisms producing vinyl and trans‐vinylene unsaturations occurred in parallel and were not influenced by the ethene or TMA concentration. In addition, some chain transfer to TMA, producing saturated end groups after hydrolysis, occurred. Copolymerizations with different additions of TMA, with the other polymerization conditions kept constant, showed that the catalytic productivity [tons of polyethylene/(mol of Zr h)], the 1‐hexene incorporation, and the molecular weight (from gel permeation chromatography) were independent of the TMA concentration. Surprisingly, the vinylidene content decreased almost linearly with increasing TMA concentration. TMA might have coordinated to the catalytic site after 1‐hexene insertion and rotation to the β‐agostic state and, therefore, suppressed the standard termination reactions after 1‐hexene insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2584–2597, 2005     

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     

Systematic Evaluation of Substituted Cyclopentadienyl Ruthenium Complexes, [(η5‐C5MenH5−n)RuCl(cod)], for Catalytic Cycloadditions of Diynes

A series of η⁵‐cyclopentadienylruthenium complexes, [(η⁵‐C₅Me_nH_5?n)RuCl(cod)] (cod=1,5‐cyclooctadiene), are evaluated as catalysts for the cycloaddition of 1,6‐diynes with alkynes. As a result, we unexpectedly found that the complex bearing the 1,2,4‐Me₃Cp ligand is the most efficient catalyst in terms of turnover number (TON) for the cycloaddition of a bulky diiododiyne with acetylene, recording the highest TON of 970 with a catalyst loading of 0.1 mol %. To obtain insight into this result, we evaluate the electron richness of all complexes by cyclic voltammetric analyses, which indicate that the electron density of the ruthenium center increases with an increase in methyl substitution on the Cp′ ligands. The initial rate (up to 10 % conversion) of the cycloaddition was then measured using ¹H NMR spectroscopy. The initial rate is found to decrease as the number of methyl substituents increases. According to these results, we assumed that the optimum catalytic performance exhibited by the 1,2,4‐trimethylcyclopentadienyl complex can be attributed to its robustness under the catalytic cycloaddition conditions. The steric and electronic effects of the Cp′ ligands are also investigated in terms of the regioselectivity of the cycloaddition of an unsymmetrical diyne and in terms of the chemoselectivity in the cycloaddition of a 1,6‐heptadiyne with norbornene.     

Efficient terpolymerization of ethylene and styrene with α‐olefins by aryloxo‐modified half‐titanocene‐based catalysts and cocatalyst systems

Aryloxo‐modified half‐titanocenes, Cp′TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) [Cp′ = Cp* ( 1 ), ^tBuC₅H₄ ( 2 )], catalyze terpolymerization of ethylene and styrene with α‐olefin (1‐hexene and 1‐decene) efficiently in the presence of cocatalyst, affording high‐molecular‐weight polymers with unimodal distributions (compositions). Efficient comonomer incorporations have been achieved by these catalysts. The content of each comonomer (α‐olefin, styrene, etc.) could be controlled by varying the comonomer concentration charged, and resonances ascribed to styrene and α‐olefin repeated insertion were negligible. The terpolymerization with p‐methylstyrene (p‐MS) in place of styrene also proceeded in the presence of [PhN(H)Me₂][B(C₆F₅)₄] and AlⁱBu₃ cocatalyst, and p‐MS was incorporated in an efficient matter, affording high‐molecular‐weight polymers with uniform molecular weight distributions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2565–2574     

Ethylene/α‐olefin copolymerization with bis(β‐enaminoketonato) titanium complexes activated with modified methylaluminoxane

Copolymerizations of ethylene with α‐olefins (i.e., 1‐hexene, 1‐octene, allylbenzene, and 4‐phenyl‐1‐butene) using the bis(β‐enaminoketonato) titanium complexes [(Ph)NC(R₂)CHC(R₁)O]₂TiCl₂ ( 1a : R₁ = CF₃, R₂ = CH₃; 1b : R₁ = Ph, R₂ = CF₃; and 1c : R₁ = t‐Bu, R₂ = CF₃), activated with modified methylaluminoxane as a cocatalyst, have been investigated. The catalyst activity, comonomer incorporation, and molecular weight, and molecular weight distribution of the polymers produced can be controlled over a wide range by the variation of the catalyst structure, α‐olefin, and reaction parameters such as the comonomer feed concentration. The substituents R₁ and R₂ of the ligands affect considerably both the catalyst activity and comonomer incorporation. Precatalyst 1a exhibits high catalytic activity and produces high‐molecular‐weight copolymers with high α‐olefin insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6323–6330, 2005     

Quasi‐living copolymerization of ethylene with 1‐hexene by heteroligated (salicylaldiminato β‐enaminoketonato) titanium complexes

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH = N(C₆F₅)] [PhN = C(R₁)CHC(R₂)O]TiCl₂ [ 3a : R₁ = CF₃, R₂ = ^tBu; 3b : R₁ = Me, R₂ = CF₃; 3c : R₁ = CF₃, R₂ = Ph; 3d : R₁ = CF₃, R₂ = C₆H₄Ph(p ); 3e : R₁ = CF₃, R₂ = C₆H₄Ph(o ); 3f : R = CF₃, R₂ = C₆H₄Cl(p ); 3g : R₁ = CF₃; R₂ = C₆H₃Cl₂(2,5); 3h : R₁ = CF₃, R₂ = C₆H₄Me(p )] were investigated as catalysts for ethylene (co)polymerization. In the presence of modified methylaluminoxane as a cocatalyst, these complexes showed activities about 50%–1000% and 10%–100% higher than their corresponding bis(β‐enaminoketonato) titanium complexes for ethylene homo‐ and ethylene/1‐hexene copolymerization, respectively. They produced high or moderate molecular weight copolymers with 1‐hexene incorporations about 10%–200% higher than their homoligated counterpart pentafluorinated FI‐Ti complex. Among them, complex 3b displayed the highest activity [2.06 × 10⁶ g/mol_Ti?h], affording copolymers with the highest 1‐hexene incorporations of 34.8 mol% under mild conditions. Moreover, catalyst 3h with electron‐donating group not only exhibited much higher 1‐hexene incorporations (9.0 mol% vs. 3.2 mol%) than pentafluorinated FI‐Ti complex but also generated copolymers with similar narrow molecular weight distributions (M _w/M _n = 1.20–1.26). When the 1‐hexene concentration in the feed was about 2.0 mol/L and the hexene incorporation of resultant polymer was about 9.0 mol%, a quasi‐living copolymerization behavior could be achieved. ¹H and ¹³C NMR spectroscopic analysis of their resulting copolymers demonstrated the possible copolymerization mechanism, which was related with the chain initiation, monomer insertion style, chain transfer and termination during the polymerization process. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2787–2797     

Higher α‐olefin polymerizations catalyzed by rac‐Me2Si(1‐C5H2‐2‐CH3‐4‐tBu)2Zr(NMe2)2/Al(iBu)3/[Ph3C][B(C6F5)4]

Polymerizations of higher α‐olefins, 1‐pentene, 1‐hexene, 1‐octene, and 1‐decene were carried out at 30 °C in toluene by using highly isospecific rac‐Me₂Si(1‐C₅H₂‐2‐CH₃‐4‐^t Bu)₂Zr(NMe₂)₂ (rac‐1) compound in the presence of Al(iBu)₃/[CPh₃][B(C₆F₅)₄] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the π‐ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(α‐olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1‐hexene), and then increased from poly(1‐hexene) to poly(1‐decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1‐pentene) > poly(1‐hexene) > poly(1‐octene) > poly(1‐decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). ¹H NMR analysis showed that vinylidene group resulting from β‐H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1687–1697, 2000     

Dramatic electronic effect of fluoro substituents on the olefin polymerization activity of mono β‐diiminato titanium complexes

A series of new mono β‐diiminato titanium complexes [(N(Ar)C(CH₃))₂ CH]TiCl₃ ( 3a : Ar = 2.6‐F₂C₆H₃; 3b : Ar = C₆F₅; 3c : Ar = 2.6‐Me₂C₆H₃) have been synthesized and characterized. The crystal structure of 3a revealed that the β‐diiminato ligand in our complex is more close to the η²‐coordination mode with little delocalization of the double bonds, which is different from the strong delocalization in the ligands of η⁵‐coordinated (Tolnacnac)TiCl₃ and η²‐coordinated (Dipnacnac)ZrCl₃. The significant electronic effects of fluoro‐substituents on the olefin polymerization activity of mono β‐diiminato titanium complexes were found. Titanium complexes with fluorine‐containing β‐diiminato ligands, on activation with MMAO, are extremely active catalysts for polymerization of ethylene. The activity of copolymerization of ethylene and 1‐hexene is higher than homopolymerization of ethylene and increases with the increase of 1‐hexene concentrations, which show the positive “comonomer effect.” The molar percentage of 1‐hexene incorporation and polymer microstructures can also be modulated by the initial comonomer concentrations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 211–217, 2008     

Half‐titanocene complexes bearing dianionic 6‐benzimidazolylpyridyl‐2‐carboximidate ligands: Synthesis,characterization, and their ethylene polymerization

6‐Benzimidazolylpyridyl‐2‐carboximidic half‐titanocene complexes, Cp′TiLCl (Cp′ = C₅H₅, MeC₅H₄, C₅Me₅, L = 6‐benzimidazolylpyridine‐2‐carboxylimidic, C1–C13 ), were synthesized and characterized along with single‐crystal X‐ray diffraction. The half‐titanocene chlorides containing substituted cyclopentadienyl groups, especially pentamethylcyclopentadienyl groups were more stable, while those without substituents on the cyclopentadienyl groups were easily transformed into their dimeric oxo‐bridged complexes, (CpTiL)₂O ( C14 and C15 ). In the presence of excessive amounts of methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all half‐titanocene complexes showed high catalytic activities for ethylene polymerization. The substituents on the Cp groups affected the catalytic behaviors of the complexes significantly, with less substituents favoring increased activities and higher molecular weights of the resultant polyethylenes. Effects of reaction conditions on catalytic behaviors were systematically investigated with catalytic systems of mononuclear C1 and dimeric C14 . With C1 /MAO, large MAO amount significantly increases the catalytic activity, while the temperature only has a slight effect on the productivity. In the case of C14 /MAO catalytic system, temperature above 60 °C and Al/Ti value higher than 5000 were necessary to observe good catalytic activities. In both systems, higher reaction temperature and low cocatalyst amount gave the polyethylenes with higher molecular weights. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3396–3410, 2008     

Copolymerization of propylene with higher α‐olefins in the presence of the syndiospecific catalyst i‐Pr(Cp)(9‐Flu)ZrCl2/MAO

The catalyst system i‐Pr(Cp)(9‐Flu)ZrCl₂/methylaluminoxane was used for the synthesis of random syndiotactic copolymers of propylene with 1‐hexene, 1‐dodecene, and 1‐octadecene as comonomers. An investigation of the microstructure by ¹³C NMR spectroscopy revealed that the stereoregularity of the copolymers decreased because of an increase in skipped insertions in the presence of the higher 1‐olefin. The melting temperature of the copolymers, as measured by differential scanning calorimetry (DSC), decreased linearly with increasing comonomer content independently of the comonomer nature. During the DSC heating cycle, an exothermic peak indicating a crystallization process was observed. The decrease in the crystallization temperature with higher 1‐olefin content, measured by crystallization analysis fractionation, indicated a small but significant dependence on the nature of the comonomer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 128–140, 2002     

Copolymerization of propylene with various higher α‐olefins using silica‐supported rac‐Me2Si(Ind)2ZrCl2

The copolymerization of propylene with 1‐hexene, 1‐octene, 1‐decene, and 1‐dodecene was carried out with silica‐supported rac‐Me₂Si(Ind)₂ZrCl₂ as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one‐half to one‐eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with α‐olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294–3303, 2001     

C2‐symmetry dimethylated zirconocenes activated with triisobutyl aluminum as effective homogeneous catalysts for copolymerization of olefins

We investigated the catalytic performance of both bridged unsubstituted [rac‐EtInd₂ZrMe₂, rac‐Me₂SiInd₂ZrMe₂] and 2‐substituted [rac‐Et(2‐MeInd)₂ZrMe₂), rac‐Me₂Si(2‐MeInd)₂ZrMe₂] dimethylbisindenylzirconocenes activated with triisobutyl aluminum (TIBA) as a single activator in (a) homopolymerizations of ethylene and propylene, (b) copolymerization of ethylene with propylene and hexene‐1, and (c) copolymerization of propylene with hexene‐1 (at Al_TIBA/Zr = 100‐300 mol/mol). Unsubstituted catalysts were inactive in homopolymerizations of ethylene and propylene and copolymerization of propylene with hexene‐1 but exhibited high activity in copolymerizations of ethylene with propylene and hexene‐1. 2‐Substituted zirconocenes activated with TIBA were active in homopolymerizations of ethylene and propylene and exhibited high activity in copolymerization of ethylene with propylene and hexene‐1, and in copolymerization of propylene with hexene‐1. Comparative microstructural analysis of ethylene‐propylene copolymers prepared over rac‐Me₂SiInd₂ZrMe₂ activated with TIBA or Me₂NHPhB(C₆F₅)₄ has shown that the copolymers formed upon activation with TIBA are statistical in nature with some tendency to alternation, whereas those with borate activated system show a tendency to formation of comonomer blocks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2934–2941, 2010     

High molar mass ethene/1‐olefin copolymers synthesized with acenaphthyl substituted metallocene catalysts

The influence of ligand structure on copolymerization properties of metallocene catalysts was elucidated with three C₁‐symmetric methylalumoxane (MAO) activated zirconocene dichlorides, ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐cyclopentadienyl)ZrCl₂ ( 1 ), ethylene(1‐(7, 9)‐diphenylcyclopenta‐[a]‐acenaphthadienyl‐2‐phenyl‐2‐fluorenyl)ZrCl₂ ( 2 ), and ethylene(1‐(9)‐fluorenyl‐(R)1‐phenyl‐2‐(1‐indenyl)ZrCl2 ( 3 ). Polyethenes produced with 1 /MAO had considerable, ca. 10% amount of trans‐vinylene end groups, resulting from the chain end isomerization prior to the chain termination. When ethene was copolymerized with 1‐hexene or 1‐hexadecene using 1 /MAO, molar mass of the copolymers varied from high to moderate (531–116 kg/mol) depending on the comonomer feed. At 50% comonomer feed, ethene/1‐olefin copolymers with high hexene or hexadecene content (around 10%) were achievable. In the series of catalysts, polyethenes with highest molar mass, up to 985 kg/mol, were obtained with sterically most crowded 2 /MAO, but the catalyst was only moderately active to copolymerize higher olefins. Catalyst 3 /MAO produced polyethenes with extremely small amounts of trans‐vinylene end groups and relatively low molar mass 1‐hexene copolymers (from 157 to 38 kg/mol) with similar comonomer content as 1 . These results indicate that the catalyst structure, which favors chain end isomerization, is also capable to produce high molar mass 1‐olefin copolymers with high comonomer content. In addition, an exceptionally strong synergetic effect of the comonomer on the polymerization activity was observed with catalyst 3 /MAO. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 373–382, 2008     

Rare‐earth‐metal‐initiated polymerizations of (meth)acrylates and block copolymerizations of olefins with polar monomers

The organo‐rare‐earth‐metal‐initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C₅Me₅)₂LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (>96%) poly(methyl methacrylate) (PMMA) with a high number‐average molecular weight (M_n > 1000 × 10³) and a very narrow molecular weight distribution [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) < 1.04] quantitatively in a short period. Bridged rare‐earth‐metallocene derivatives were used to perform the block copolymerization of ethylene or 1‐hexene with MMA, methyl acrylate, cyclic carbonate, or ?‐caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (M_n > 500 × 10³, M_w/M_n < 1.1) PMMA was first obtained in 1998 with [(Me₃Si)₃C]₂Yb. Stereocomplexes prepared by the mixing of the resulting syndiotactic and isotactic PMMA revealed improved physical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1955–1959, 2001     

Imino‐indolate half‐titanocene chlorides: Synthesis and their ethylene (co‐)polymerization

A series of imino‐indolate half‐titanocene chlorides, Cp′Ti(L)Cl₂ ( C1 – C7 : Cp′ = C₅H₅, MeC₅H₄, C₅Me₅, L = imino‐indolate ligand), were synthesized by the reaction of Cp′TiCl₃ with sodium imino‐indolates. All complexes were characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. Moreover, the molecular structures of two representative complexes C4 and C6 were confirmed by single crystal X‐ray diffraction analysis. On activation with methylaluminoxane (MAO), these complexes showed good catalytic activities for ethylene polymerization (up to 7.68 × 10⁶ g/mol(Ti)·h) and ethylene/1‐hexene copolymerization (up to 8.32 × 10⁶ g/mol(Ti)·h), producing polyolefins with high molecular weights (for polyethylene up to 1808 kg/mol, and for poly(ethylen‐co‐1‐hexene) up to 3290 kg/mol). Half‐titanocenes containing ligands with alkyl substituents showed higher catalytic activities, whereas the half‐titanocenes bearing methyl substituents on the cyclopentadienyl groups showed lower productivities, but produced polymers with higher molecular weights. Moreover, the copolymerization of ethylene and methyl 10‐undecenoate was demonstrated using the C1 /MAO catalytic system. The functionalized polyolefins obtained contained about 1 mol % of methyl 10‐undecenoate units and were fully characterized by several techniques such as FT‐IR, ¹H NMR, ¹³C NMR, DSC, TGA and GPC analyses. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 357–372, 2009     

In situ‐generated Ru(III)‐mediated ATRP from the polymeric Ru(III) complex in the absence of activator generation agents

Past research has examined the atom transfer radical polymerization (ATRP) with high oxidation state metal complexes and without the need for any additives such as reducing agent or free radical initiator. To extend this research, half‐metallocene ruthenium(III) (Ru(III)) catalysts were used for the polymerization of methyl methacrylate (MMA) for the first time. These catalysts were generated in situ simply by mixing phosphorus‐containing ligand and pentamethylcyclopentadienyl (Cp*) Ru(III) polymer ((Cp*RuCl₂)_n). The complexes in their higher oxidation state such as Cp*RuCl₂(PPh₃) were air‐stable, highly active, and removable catalysts for the ATRPs of MMA with both precision control of molecular weight and narrow polydispersity index. The addition of ppm amount of metal catalyst contributed to the formation of very well‐defined homopolymers and copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Copolymerization of ethylene with 1‐hexene promoted by novel multi‐chelated non‐metallocene complexes with imine bridged imidazole ligand

A series of novel bridged multi‐chelated non‐metallocene catalysts is synthesized by the treatment of N,N‐imidazole, N,N‐dimethylimidazole, and N,N‐benzimidazole with n‐BuLi, 2,6‐dimethylaniline, and MCl₄ (M = Ti, Zr) in THF. These catalysts are used for copolymerization of ethylene with 1‐hexene after activated by methylaluminoxane (MAO). The effects of polymerization temperature, Al/M molar ratio, and pressure of monomer on ethylene copolymerization behaviors are investigated in detail. These results reveal that these catalysts are favorable for copolymerization of ethylene with 1‐hexene featured high catalytic activity and high comonomer incorporation. The copolymer is characterized by ¹³C NMR, WAXD, GPC, and DSC. The results confirm that the obtained copolymer features broad molecular weight distribution (MWD) about 33–35 and high 1‐hexene incorporation up to 9.2 mol %, melting temperature of the copolymer depends on the content of 1‐hexene incorporation within the copolymer chain and 1‐hexene unit in the copolymer chain isolates by ethylene units. The homopolymer of ethylene has broader MWD with 42–46. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 417–424, 2010     

MAO‐free polymerization of propylene by rac‐ Me2Si(1‐C5H2‐2‐Me‐4‐tBu)2Zr(NMe2)2 compound

Ansa‐zirconocene diamide complex rac‐Me₂Si(CMB)₂Zr(NMe₂)₂ (rac‐1, CMB = 1‐C₅H₂‐2‐Me‐4‐^tBu) reacts with AlR₃ (R = Me, Et, i‐Bu) and then with [CPh₃]⁺[B(C₆F₅)₄]⁻ (2) in toluene in order to in situ generate cationic alkylzirconium species. In the sequential NMR‐scale reactions of rac‐1 with various amount of AlMe₃ and 2, rac‐1 transforms first to rac‐Me₂Si(CMB)₂Zr(Me)(NMe₂) (rac‐3) and rac‐Me₂Si(CMB)₂ZrMe₂ (rac‐4) by the reaction with AlMe₃, and then to [rac‐Me₂Si(CMB)₂ZrMe]⁺ (5⁺) cation by the reaction of the resulting mixtures with 2. The activities of propylene polymerizations by rac‐1/Al(i‐Bu)₃/2 system are dependent on the type and concentration of AlR₃, resulting in the order of activity: rac‐1/Al(i‐Bu)₃/2 > rac‐1/AlEt₃/2 > rac‐1/MAO ≫ rac‐1/AlMe₃/2 system. The bulkier isobutyl substituents make inactive catalytic species sterically unfavorable and give rise to more separated ion pairs so that the monomers can easily access to the active sites. The dependence of the maximum rate (R_{p, max}) on polymerization temperature (T_p) obtained by rac‐1/Al(i‐Bu)₃/2 system follows Arrhenius relation, and the overall activation energy corresponds to 0.34 kcal/mol. The molecular weight (MW) of the resulting isotactic polypropylene (iPP) is not sensitive to Al(i‐Bu)₃ concentration. The analysis of regiochemical errors of iPP shows that the chain transfer to Al(i‐Bu)₃ is a minor chain termination. The 1,3‐addition of propylene monomer is the main source of regiochemical sequence and the [mr] sequence is negligible, as a result the meso pentad ([mmmm]) values of iPPs are very high ([mmmm] > 94%). These results can explain the fact that rac‐1/Al(i‐Bu)₃/2 system keeps high activity over a wide range of [Al(i‐Bu)₃]/[Zr] ratio between 32 and 3,260. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1071–1082, 1999