Synthesis and oxidative degradation of poly(ethene‐ran‐1,3‐butadiene)

Copolymerization of ethene and 1,3‐butadiene was conducted over SiO₂‐supported CpTiCl₃ catalyst using Ph₃CB(C₆F₅)₄ or B(C₆F₅)₃ combined with triisobutylaluminium (ⁱBu₃Al) or trioctylaluminium (Oct₃Al). When the copolymerization was carried out at 0°C, the Ph₃CB(C₆F₅)₄/ⁱBu₃Al and B(C₆F₅)₃/Oct₃Al systems selectively produced copolymers which contained about 0.5–2.5 mol‐% of trans‐1,4‐inserted butadiene units. The number‐average molecular weight (M_n) of the copolymers was around 80 000 with polydispersities in the range from 6 to 8. Oxidative degradation of the vinylene units with potassium permanganate decreased the M_n values to several thousands with polydispersities of ca. 2. This indicates that the butadiene units are randomly distributed in the copolymers. NMR analysis clarified that the decomposed product is a polyethene with carboxyl groups at both chain ends.     

Functionalization of vinylic addition polynorbornenes via efficient copolymerization of norbornene using Ni(II)‐Me complexes

The facile and efficient functionalization of polynorbornene has been achieved through direct copolymerization of norbornene (NB) with 5‐norbornene‐2‐yl acetate (NBA) or 5‐norbornene‐2‐methanol (NBM) using a series of β‐ketiminato Ni(II)‐Me pyridine complexes 1–4 (Scheme 2 ) in the presence of B(C₆F₅)₃. Remarkably, the monomer conversion could reach up to about 96% in 10 min in the NB/NBA copolymerization. The copolymers with wide NBA contents (3.3–38.4 mol %) were obtained by variation of reaction conditions. These copolymers have high molecular weights (MWs) (M_n = 41.8–144 kg/mol) and narrow MW distributions (M_w/M_n = 1.80–2.27). In the absence of alkyl aluminum compounds, a monomer conversion of 81% was observed in the NB/NBM copolymerization, and copolymers with NBM content in the range of 11.2–21.8 mol % were obtained by variation of reaction conditions. In addition, Ni(II)‐Me pyridine complexes 2 was very active at a low B/Ni molar ratio of 6, while bis‐ligand complex 6 bearing the same ligand just showed moderate efficiency at a high B/Ni molar ratio of 20. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Living copolymerization of ethylene with norbornene mediated by heteroligated (Salicylaldiminato)(β‐enaminoketonato)titanium catalysts

Three heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH?N(C₆F₅)][(p‐XC₆H₄)N?C(Bu^t)CHC(CF₃)O]TiCl₂ ( 3a : X = F, 3b : X = Cl, 3c : X = Br) were synthesized and investigated as the catalysts for ethylene polymerization and ethylene/norbornene copolymerization. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts exhibited high activities toward ethylene polymerization, similar to their parallel parent catalysts. Furthermore, they also displayed favorable ability to efficiently incorporate norbornene into the polymer chains and produce high molecular weight copolymers under the mild conditions, though the copolymerization of ethylene with norbornene leads to relatively lower activities. The sterically open structure of the β‐enaminoketonato ligand is responsible for the high norbornene incorporation. The norbornene concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. When the norbornene concentration in the feed is higher than 0.4 mol/L, the heteroligated catalysts mediated the living copolymerization of ethylene with norbornene to form narrow molecular weight distribution copolymers (M_w/M_n < 1.20), which suggested that chain termination or transfer reaction could be efficiently suppressed via the addition of norbornene into the reaction medium. Polymer yields, catalytic activity, molecular weight, and norbornene incorporation can be controlled within a wide range by the variation of the reaction parameters such as comonomer content in the feed, reaction time, and temperature. ©2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6072–6082, 2009     

Controlled ring‐opening polymerization of l‐lactide and ε‐caprolactone catalyzed by aluminum‐based Lewis pairs or Lewis acid alone

Ring‐opening polymerization of cyclic esters was studied using catalysts composed of bulky Lewis acids (LA) and Lewis bases (LB). Controlled polymerization of l ‐lactide (l ‐Lac) was proceeded by Al(C₆F₅)₃·THF in combination with trimesitylphosphine (Mes₃P) or triphenylphosphine (Ph₃P) using BnOH as an initiator to produce poly(l ‐Lac) with narrow molecular weight distribution (MWD; M_w/M_n = 1.1). Both the LA and the LB were indispensable to promote the polymerization. The molecular weights of the resulting poly(l ‐Lac)s were controlled by the feed monomer to initiator ratio. ε‐Caprolactone (CL) was rapidly polymerized by Al(C₆F₅)₃·THF with or without Mes₃P, although the resulting polymer had rather broad MWD (M_w/M_n = 1.7). The CL polymerization by Al(C₆F₅)₃·THF alone at r.t. gave poly(CL) with relatively narrow MWD (M_w/M_n = 1.2). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 297–303     

Synthesis of bromine-functionalized polyolefins by scandium-catalyzed copolymerization of 10-bromo-1-decene with ethylene,propylene, and dienes

By use of a THF-containing trimethylsilylmethyl scandium catalyst system (C₅Me₄SiMe₃)Sc(CH₂SiMe₃)₂(THF)/[Ph₃C][B(C₆F₅)₄], the multi-component copolymerization of 10-bromo-1-decene (BrDC) with ethylene, propylene, and dienes has been achieved to afford a new family of bromine-functionalized polyolefins with controllable composition and high molecular weight. The copolymerization of BrDC with ethylene afforded the well-defined BrDC–ethylene copolymers with high BrDC incorporation (up to 12 mol%) and high molecular weight (M_w > 100 kg mol⁻¹). The terpolymerization of propylene, ethylene with BrDC afforded random ethylene–propylene–BrDC terpolymers with controllable bromine content (2 ~ 11 mol%), high molecular weight (M_w > 100 kg mol⁻¹) and low glass transition temperature (T_g = −51 °C ~ −67 °C). Moreover, the tetrapolymerization of ethylene, propylene, BrDC, and ethylidene norbornene or conjugated dienes such as isoprene and myrcene has been achieved for the first time to afford selectively the bromine-functionalized ethylene–propylene–diene rubbers containing various types of double bonds.     

Synthesis and characterization of materials prepared via the copolymerization of ethylene with 1‐octadecene and norbornene using a [(π‐cyano‐nacnac)Cp] zirconium complex

[3‐Cyano‐2‐(2,6‐diisopropylphenyl)aminopent‐2‐en‐4‐(phenylimine)tris (pentafluorophenyl)borate](η⁵‐C₅H₅)ZrCl₂, [(B(C₆F₅)₃‐ NC‐nacnac)CpZrCl₂], precatalyst ( 2 ) can be treated with low concentrations of methylaluminoxane (MAO) to generate active sites capable of copolymerizing ethylene with 1‐octadecene or norbornene under mild conditions. A series of poly(ethylene‐co‐octadecene) and poly(ethylene‐co‐norbornene) copolymers were prepared, and their properties were characterized by NMR, differential scanning calorimetry, and mechanical analysis. The results show that this system produced poly(ethylene‐co‐octadecene) copolymers with a branching content of about 8 mol %. However, upon increasing the comonomer concentration, a drastic reduction in the M_n of the product is observed concomitant with an increase in comonomer incorporation. This leads to a gradual decrease in Young's modulus and stress at break, indicating an increase in the “softness” of the copolymer. In the case of copolymerizations of ethylene and norbornene, the catalytic system ( 2 /MAO) shows a substantial decrease in reactivity in the presence of norbornene and generates copolymer chains in which 5–10 mol % norbornene is in blocks. We also observe that ethylene norbornene copolymers exhibit a high degree of alternating insertions (close to 50%), as determined by NMR spectroscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A non‐PFT (polymerization filling technique) approach to poly(ethylene‐co‐norbornene)/MWNTs nanocomposites by in situ copolymerization with scandium half‐sandwich catalyst

The in situ synthesis of ethylene‐co‐norbornene copolymers/multi‐walled carbon nanotubes (MWNTs) nanocomposites was achieved by rare‐earth half‐sandwich scandium precursor [Sc(η⁵‐C₅Me₄SiMe₃)(η¹‐CH₂SiMe₃)₂(THF)] (1) activated by [Ph₃C][B(C₆F₅)₄], through a non‐PFT (Polymerization Filling Technique) approach. MWNTs nanocomposites with low aluminum residue were obtained with excellent yields even though small amounts of triisobutylaluminium were needed as scavenger to prevent catalyst poisoning by MWNT impurities. MWNT bundles were disaggregated and highly coated with Poly(ethylene‐co‐norbornene) [P(E‐co‐N)] as revealed by transmission electron microscopy. Interestingly, P(E‐co‐N) copolymers showed T_g over 130 °C as well as norbornene content over 50 mol %; both values were higher than those obtained by the cationic active species in 1 /[Ph₃C][B(C₆F₅)₄]. A series of copolymerization reactions by 1 /[Ph₃C][B(C₆F₅)₄]/AlⁱBu₃ without MWNTs produced copolymers with the same unexpected features. The NMR analysis revealed the presence of rac‐ENNE and rac‐ENNNE sequences. Thus, AlⁱBu₃ changed the stereoirregular alternating copolymer microstructure produced by 1 /[Ph₃C][B(C₆F₅)₄]. We conclude that AlⁱBu₃ is not only a scavenger for CNT impurities, but it reacts with the THF ligand to give coordinatively unsaturated active species. Finally, P(E‐co‐N)/MWNT masterbatches were mixed with commercial TOPAS to produce cyclic olefin copolymer nanocomposites with excellent dispersion of filler. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5709–5719, 2009     

Styrene‐vinylferrocene random and block copolymers by TEMPO‐mediated radical polymerization

TEMPO‐mediated free radical polymerization was employed for homo‐ and copolymerization of vinylferrocene (Vfc). Homopolymerization of Vfc resulted in relatively narrow polydispersities (M_w/M_n = 1.24–1.8), however, molecular weights were limited to 4 800. Copolymerization with styrene afforded random copolymers with molecular weights (M_n) up to 10 000, narrow polydispersity (1.2 > M_w/M_n > 1.4) and up to 42 mol‐% Vfc. Block copolymers with PS block and P(S‐co‐Vfc) block with molecular weights (M_n) in the range of 9 000 to 17 600 (M_w/M_n > 1.3) were also prepared with up to 17 mol‐% vinylferrocene. DSC revealed two glass transition temperatures (T_g) evidencing phase separation.     

Polymerization of 1‐hexene with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride using iBu3Al/Ph3CB(C6F5)4 as a cocatalyst

1‐Hexene polymerization was investigated with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride ( 1 ) using ⁱBu₃Al/Ph₃CB(C₆F₅)₄ as a cocatalyst. This catalyst system produced poly(1‐hexene) having a high molecular weight (M_w = 445 000–884 000, 0–60°C). ¹³C NMR spectroscopy revealed that the high molecular weight poly(1‐hexene) possesses an atactic structure with about 50 mol‐% of regioirregular units.     

Copolymerization of norbornene and 5‐norbornene‐2‐yl acetate using novel bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3 catalytic system

Vinyl‐type copolymerization of norbornene (NBE) and 5‐NBE‐2‐yl‐acetate (NBE‐OCOMe) in toluene were investigated using a novel homogeneous catalyst system based on bis(β‐ketonaphthylamino)Ni(II)/B(C₆F₅)₃/AlEt₃. The copolymerization behavior as well as the copolymerization conditions, such as the levels of B(C₆F₅)₃ and AlEt₃, temperature, and monomer feed ratios, which influence on the copolymerization were examined. Without combination of AlEt₃, the catalytic bis(β‐ketonaphthylamino)Ni(II)/B(C₆F₅)₃ exhibited very high catalyst activity for polymerization of NBE. Combination of AlEt₃ in catalyst system resulted in low conversion for polymerization of NBE. For copolymerization of NBE and NBE‐OCOMe, involvement of AlEt₃ in catalyst is necessary. Slight addition of NBE‐OCOMe in copolymerization of NBE and NBE‐OCOMe gives rise to significant increase of catalyst activity for catalytic system bis(β‐ketonaphthylamino)Ni(II)/B(C₆F₅)₃/AlEt₃. Nevertheless, excess increase of the NBE‐OCOMe content in the comonomer feed ratios results in decrease of conversion as well as activity of catalyst. The achieved copolymers were confirmed to be vinyl‐addition copolymers through the analysis of FTIR, ¹H NMR, and ¹³C NMR spectra. ¹³C NMR studies further revealed the composition of the copolymer and the incorporation rate was 7.6–54.1 mol % ester units at a content of 30–90 mol % of the NBE‐OCOMe in the monomer feeds ratios. TGA analysis results showed that the copolymer exhibited good thermal stability (T_d > 410 °C) and failed to observe the glass transitions temperature over 300 °C. The copolymers are confirmed to be noncrystalline by WAXD analysis results and show good solubility in common organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3990–4000, 2009     

Syndiospecific living polymerization of 4‐methylstyrene and styrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminum catalytic system

The polymerizations of styrene and 4‐methylstyrene (4MS) with a half‐metallocene type catalytic system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe₃), trioctylaluminum (AlOct₃), and tris(pentafluorophenyl)borane [B(C₆F₅)₃] were investigated at ?25 °C. The addition of AlOct₃ as a third component of the catalytic system is effective both to promote the syndiospecific polymerization and to inhibit the nonstereospecific polymerization at the low‐temperature region. The use of AlOct₃ was also effective to eliminate the chain transfer reaction to alkylaluminum. The number‐average molecular weights (M_n's) of poly(4MS) or polystyrene increased proportionally with increasing monomer conversion. The molecular weight distribution (MWD) of polymer stayed narrow [M_w/M_n = ～ 1.1 for poly(4MS) and M_w/M_n = ～ 1.5 for polystyrene]. It was thus concluded that the polymerizations of the styrenic monomers with Cp*TiMe₃/B(C₆F₅)₃/AlOct₃ catalytic system proceeded under living fashion at ?25 °C. The living random copolymerization behaviors of styrene and 4MS were also confirmed. The ¹³C NMR analysis clarified that each of the homopolymers and random copolymers obtained in this work had highly syndiotactic structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3692–3706, 2001     

Copolymerization of 2‐butene and ethylene with catalysts based on titanium and zirconium complexes

The polymerization of 2‐butene and its copolymerization with ethylene have been investigated using four kinds of dichlorobis(β‐diketonato)titanium complexes, [ArN(CH₂)₃NAr]TiCl₂ (Ar = 2,6‐ⁱPr₂C₆H₃) and typical metallocene catalysts. The obtained copolymers display lower melting points than those produced of homopolyethylene under the same polymerization conditions. ¹³C NMR analysis indicates that 9.3 mol‐% of 2‐butene units were incorporated into the polymer chains with Ti(BFA)₂Cl₂‐MAO as the catalyst system. With the trans‐2‐butene a higher copolymerization rate was observed than with cis‐2‐butene. A highly regioselective catalyst system for propene polymerization, [ArN(CH₂)₃NAr]TiCl₂ complex using a mixture of triisobutylaluminium and Ph₃CB(C₆F₅)₄ as cocatalyst, was found to copolymerize a mixture of 1‐butene and trans‐2‐butene with ethylene up to 3.1 mol‐%. Monomer isomerization‐polymerization proceeds with typical metallocene catalysts to produce copolymers consisting of ethylene and 1‐butene.     

Block copolymerization of allene derivatives with 1,3-butadiene by living coordination polymerization with π-allylnickel catalyst

The block copolymerization of allene derivatives (3A–3D) with 1,3-butadiene (2) by [(allyl)NiOCOCF₃]₂ (1) is described. For instance, the living coordination polymerization of phenylallene (3A, 50 equiv) starting from the living poly(2), which was prepared by the polymerization of 2 (160 equiv) by 1, successfully gave a block copolymer of 2 and 3A in high yield. The molecular weight of the block copolymer (4A) in gel permeation chromatography shifted clearly to the higher molecular weight region and kept a unimodal distribution (M_n = 17,400, M_w/M_n = 1.23) in comparison with that of the starting living poly(2) (M_n = 5,600, M_w/M_n = 1.67). The ratio of each segment and the molecular weight of the resulting copolymers could be controlled by the feed ratio of each monomer. The block copolymerization also proceeded successfully by the inverse order of the monomer feeding (i.e., the polymerization of 3A followed by that of 2) to obtain the corresponding block copolymers in high yields. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3916–3921, 1999     

Ni(II) and Pd(II) complexes bearing novel bis(β‐ketoamino) ligand and their catalytic activity toward copolymerization of norbornene and 5‐norbornene‐2‐yl acetate combined with B(C6F5)3

Two complexes Mt{C₁₀H₈(O)C[N(C₆H₅)]CH₃}₂ [Mt = Ni(II); Mt = Pd(II)] were synthesized, and the solid‐state structures of the complexes have been determined by single‐crystal X‐ray diffractions. Homopolymerization of norbornene (NB) and copolymerization of NB and 5‐norbornene‐2‐yl acetate (NB‐OCOCH₃) were carried out in toluene with both the two complexes mentioned above in combination with B(C₆F₅)₃. Both the catalytic systems exhibited high activity toward the homopolymerization of NB (as high as 2.7 × 10⁵ g_polymer/mol_Ni h, for Ni(II)/B(C₆F₅)₃ and 2.1 × 10⁵ g_polymer/mol_Pd h for Pd(II)/B(C₆F₅)₃, respectively.). Although the Pd(II)/B(C₆F₅)₃ shows very lower activity toward the copolymerization of NB with NB‐OCOCH₃, Ni(II)/B(C₆F₅)₃ shows a high activity and produces the addition‐type copolymer with relatively high molecular weights (MWs; 1.80–2.79 × 10⁵ g/mol) as well as narrow MW distribution (1.89–2.30). The NB‐OCOCH₃ content in the copolymers can be controlled up to 5.8–12.0% by varying the comonomer feed ratios from 10 to 50%. The copolymers exhibited high transparency, high glass transition temperature (T_g > 263.9 °C), better solubility, and mechanical properties compared with the homopolymer of NB. The reactivity ratios of the two monomers were determined to be r_NB‐OCOMe = 0.08, r_NB = 7.94 for Ni(II)/B(C₆F₅)₃ system, and r_NB‐OCOMe = 0.07, r_NB = 6.49, for Pd(II)/B(C₆F₅)₃ system by the Kelen‐Tüdõs method. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L‐proline)‐block‐poly(ε‐caprolactone) copolymers

A series of novel types of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline)‐block‐poly(ε‐caprolactone) (PHpr‐b‐PCL) copolymers were successfully synthesized via melt block copolymerization of trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) and ε‐caprolactone (ε‐CL) with a trifunctional initiator trimethylolpropane (TMP) and stannous octoate (SnOct₂) as a catalyst. For the homopolycondensation of N‐CBz‐Hpr with TMP initiator and SnOct₂ catalyst, the number‐average molecular weight (M_n) of prepolymer increases from 530 to 3540 g mol^?1 with the molar ratio of monomer to initiator (3–30), and the molecular weight distribution (M_w/M_n) is between 1.25 to 1.32. These three‐armed prepolymer PHpr were subsequently block copolymerized with ε‐caprolactone (ε‐CL) in the presence of SnOct₂ as a catalyst. The M_n of the copolymer increased from 2240 to 18,840 g mol^?1 with the molar ratio (0–60) of ε‐CL to PHpr. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass‐transition temperature (T_g) of the three‐armed polymers depended on the molar ratio of monomer/initiator that were added. In vitro degradation of these copolymers was evaluated from weight‐loss measurements and the change of M_n and M_w/M_n. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1708–1717, 2005     

Ru(II)‐mediated living radical polymerization: block and random copolymerizations of N,N‐dimethylacrylamide and methyl methacrylate

RuCl₂(PPh₃)₃ led to living radical copolymerization of N,N‐dimethylacrylamide (DMAA) and methyl methacrylate (MMA) in conjunction with a halide‐initiator (R‐X; CHCl₂COPh, CCl₃Br) and Al(Oi‐Pr)₃ in toluene at 80°C. Both the monomers were polymerized at almost the same rate into random copolymers, where the number‐average molecular weights (M_n) increased in direct proportion to weight of the obtained polymers, and the molecular weight distributions (MWDs) were narrow throughout the reactions (M_w/M_n = 1.2‐1.6). MMA was consumed faster in the copolymerization than in the homopolymerization, which was due to the interaction of DMAA with the ruthenium complex. The Ru(II)‐based initiating system was also effective in block copolymerization of DMAA and MMA.     

Synthesis of Pd catalysts based on a nonbornene−CO copolymer and their properties in the carbomethoxylation of propylene

It was found that carboxylation of norbornene (nbn) in the presence of the PdCl₂−PPh₃−HCl catalytic system is accompanied by alternating copolymerization ofnbn with carbon monoxide to form norbornanecarboxylic acid (yield ∼20%) and anbn-CO copolymer (yield ∼80%,M _w=1600,M _w/M _n=1.6). The Pd^II salt of poly(norbornaneketone)carboxylic acid is a highly active catalyst for the carbomethoxylation of propylene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 368–370, February, 1998.     

Ethylene–Norbornene Copolymerization by Rare-Earth Metal Complexes and by Carbon Nanotube-Supported Metallocene Catalysis

E–N copolymerization with a number of half-sandwich rare-earth metal compounds [M(η5-C₅Me₄SiMe₂R)(η1-CH₂SiMe₃)₂(L)] (M = Sc, Y, Lu) has been achieved. Mainly atactic alternating E N copolymers are obtained with all catalytic systems. Interestingly, copolymers arising from [Sc(η5-C₅Me₄SiMe₂C₆F₅)(η¹-CH₂SiMe₃)₂(THF)]/[/[Ph₃C][B(C₆F₅)₄] possess narrower molar mass distributions than those from [Sc(η⁵-C₅Me₄SiMe₃)(η¹-CH₂SiMe₃)₂(THF)] / [Ph₃C][B(C₆F₅)₄]. In addition, homogeneous surface coating of multi-walled carbon nanotubes is accomplished for the first time by in situ E–N copolymerization as catalyzed by rac-Et(Ind)₂ZrCl₂/MMAO-3A anchored onto the carbon nanotube surface. The copolymerization reaction allows for the destructuration of the native nanotube bundles. The relative quantity of E N copolymer can be tuned up as well as the norbornene content in the formed copolymers and accordingly their glass transition temperature. By melt blending with an ethylene-vinyl-co-acetate copolymer (27 wt.-% vinyl acetate comonomer) matrix, high performance polyolefinic nanocomposites are obtained.     

Low-temperature isospecific polymerization of propylene catalyzed by alkylzirconocene-type ‘cations’

The rac-ethylenebis(indenyl)methylzirconium ‘cation’ (1), generated from rac-Et(Ind)₂ZrMe₂ and Ph₃CB(C₆F₅)₄, has recently been shown to be exceedingly active and stereoselective in propylene polymerization. The ethyl analog (2) can be produced by an alternate, efficient route involving a reaction between rac-Et(Ind)₂ZrCl₂ and AlEt₃ (TEA), followed by addition of Ph₃CB(C₆F₅)₄. The use of excess AlEt₃ serves both to alkylate the zirconium complex as well as to scavenge the system. The propylene polymerization activity of the ‘cation’ 2 is about 7000 times greater than the activity of rac-Et(Ind)₂ZrCl₂/methylaluminoxane (MAO) at T_p=?20°C. The related catalyst system rac-Me₂Si(Ind)₂ZrCl₂/TEA/Ph₃CB(C₆F₅)₄ (3) was found to produce 98.3% i-PP with T_m 156.3°C and an activity of 1.8 × 10⁹ g PP {(mol Zr) [C₃H₆]h}^?1.     

Nickel(II) and palladium(II) complexes with α‐dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane,tris(pentafluorophenyl)borane,or triethylaluminum cocatalyst systems

Nickel(II) and palladium(II) complexes with α‐dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2‐cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo‐Lewis acid tris(pentafluorophenyl)borane [B(C₆F₅)₃], and triethylaluminum (TEA) AlEt₃. The palladium but not the nickel precatalysts could also be activated by B(C₆F₅)₃ alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 10⁷ g_polymer/mol_metal · h. With the system B(C₆F₅)₃/AlEt₃, the activation process can be formulated as the following two‐step reaction: (1) B(C₆F₅)₃ and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C₆F₅)_nEt_3?n and B(C₆F₅)_3?nEt_n; and (2) Al(C₆F₅)_nEt_3?n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C₆F₅)Et₂ is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1‐dodecene as chain‐transfer agents; the molar mass can be varied in the number‐average molecular weight range from 2 · 10³ to 9 · 10⁵ g · mol^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604–3614, 2002