A novel half-sandwich titanium complex, Cp*Ti(1-C10H7O)Cl2, containing an α-naphthoxide fragment, was synthesized. Modified methylaluminoxane (MMAO-12) and perfluoroaryl boron-containing activators B(C6F5)3 and [Ph3C][B(C6F5)4] combined with triisobutylaluminum were used to activate the precatalyst. The resulting catalysts produced binary and ternary copolymers of ethylene with propylene and 5-ethylidene-2-norbornene. The composition, molecular weight characteristics, and thermophysical properties of the copolymers—including those of ethylene/propylene copolymer samples after stepwise isothermal melt crystallization—were characterized. The copolymerization performance of the catalysts was compared with previously studied similar systems based on the half-sandwich titanium complex Cp*Ti(O2,6iPr2C6H3)Cl2. The properties of the copolymers were also assessed comparatively. The synthesized catalytic systems produced polymer mixtures consisting of low-molecular-weight (comonomer-enriched) fractions and high-molecular-weight polyethylene fractions, likely due to the generation of two different types of active sites responsible for producing bimodal copolymers.

This review provides an analysis of prior research on the kinetics of the trimerization of ethylene to 1-hexene over existing chromium-based catalytic systems. It discusses the known mechanisms and reaction steps for the formation of 1-hexene as well as olefin by-products. The effects of catalytic system composition, temperature, pressure, reaction time, and the presence of hydrogen on the kinetics of 1-hexene formation are also touched upon. The kinetic models of ethylene trimerization to 1-hexene known from published literature are presented.

Half-sandwich titanium complexes, specifically Cp*TiCl3 and Cp*Ti[O(2,6-iPr2-Ph)]Cl2, were investigated as catalytic precursors for the synthesis of ethylene/propylene copolymers and ethylene/propylene/5-ethylidene-2-norbornene terpolymers. For this purpose, a variety of activators were tested: modified polymethylaluminoxane; boron-containing compounds such as B(C6F5)3 and Ph3CB(C6F5)4 in combination with triisobutylaluminum (TIBA); isobutylaluminoxane (IBAO), and isobutylaluminum aryloxide (2,6-tBu2,4-Me-PhO-)AliBu2 (AlBHT). In the copolymerization of ethylene and propylene, the catalysts exhibited high activity when activated by MMAO-12 and TIBA+Ph3CB(C6F5)4 but low activity with TIBA+B(C6F5)3 and AlBHT. With IBAO as an activator, these catalysts were found to be totally ineffective. The catalysts exhibited low activity in terpolymerization. It was further revealed that more than one type of active sites was generated in the catalytic systems: these sites were responsible for simultaneous formation of low-molecular-weight and ultrahigh-molecular-weight polymers. The composition of the copolymers as well as their thermophysical and physicomechanical properties were shown to depend on the type and composition of the catalytic system.

Ethylene/propylene (E/P) and ethylene/propylene/5-ethylidene-2-norbornene (E/P/ENB) copolymers were obtained on rac-Et(2-MeInd)2ZrMe2 activated by a number of isobutylaluminium aryloxides: (2,6-tBu2PhO-)AliBu2 (1-DTBP) (2,6-tBu2,4-Me-PhO-)AliBu2 (1-BHT), (2,4,6-tBu2PhO-)AliBu2 (1-TTBP), (2,6-tBu2,4-Me-PhO-)2AliBu (2-BHT), (2,6-tBu2PhO-)2AliBu (2-DTBP), [(2-Me,6-tBu-C6H3O)AliBu2]2 (1-MTBP), [(2,6-Ph2-PhO)AliBu2]2 (1-DPP). This study shows how the structure of an activator influences catalytic activity and polymer properties, such as the copolymer composition, molecular weight characteristics, and thermophysical and mechanical properties. It has been shown that both the introduction of a bulky substituent in the para-position of the aryloxy group and the additional aryloxy group in the structure of an activator lead to a significant decrease in activity of the catalytic system in all studied copolymerization processes. Moreover, activation by bulkier aryloxides leads to lower levels of comonomer insertion and gives rise to higher molecular weight polymers. Broad or multiple endothermic peaks with different values of melting points are observed on the DSC curves of the copolymers obtained with different catalytic systems. The DSC of the thermally fractionated samples makes it possible to reveal the heterogeneity of the copolymer microstructure, which manifests itself in the presence of a set of lamellar crystallites of different thickness. The results also present the mechanical properties of the copolymers, such as the tensile strength (σ), elongation at break (ε), and engineering strain (EL). The synthesized E/P and E/P/ENB copolymers contain about 1–4 wt.% of the sterically hindered phenols obtained in situ as a residue of the hydrolyzed activators in the course of reaction quenching. This determines the increased thermooxidative stability of the copolymers.

Ethylene-propylene-diene rubbers (EPDM) are one of the most important polyolefin materials widely commercialized and used in various industries in recent years. The production of EPDM is based solely on catalytic coordination polymerization processes. The development of new catalysts and processes for the synthesis of EPDM has expanded the range of products and their manufacturing in terms of energy efficiency, processability, and environmental safety. This mini-review mainly analyzes patented data on the synthesis of EPDM on new-generation single-site catalytic systems based on Group IVB complexes including the systems commercialized by major manufacturers of EPDM. The advantages of these systems are evident in comparison with conventional vanadium systems introduced into production in the 1960s and used to date in the industrial synthesis of EPDM.

This work explores new catalytic systems for the synthesis of ethylene-propylene (EPM) and ethylene-propylenediene (EPDM) copolymers. We present the results on ethylene/propylene copolymerization and terpolymerization of ethylene/propylene/5-ethylidene-2-norbornene with different metallocenes activated by (2,6-tBu2PhO-) AliBu2. Metallocenes employed are EtInd2TiMe2, rac-EtInd2ZrMe2, rac-EtInd2HfMe2, rac-Et(2-MeInd)2ZrMe2, racMe2Si(2-MeInd)2ZrMe2. The data encompasses catalytic performance of the systems and copolymers properties: composition, molecular weight, thermo-physical, and mechanical characteristics. The highest copolymerization activities were observed for zirconocenes, the lowest ? for rac-EtInd2HfMe2. On the other hand, rac-EtInd2HfMe2 shows the best incorporation of both propylene and 5-ethylidene-2-norbornene, yielding polymers with high molecular weights, low crystallinities and melting points. This catalyst system demonstrated the possibility of producing terpolymers with propylene content up to 39 wt % and 5-ethylidene-2-norbornene up to 18 wt %. Copolymers of ethylene with propylene with the highest tensile strength and elongation at break are obtained on rac-Me2Si(2-MeInd)2ZrMe2, while terpolymer with good elastic properties is formed on rac-EtInd2ZrMe2 and racEtInd2HfMe2. Copolymers with the best relaxation properties were synthesized on rac-EtInd2HfMe2.

The studies devoted to the synthesis of ternary copolymers of ethylene, propylene, and nonconjugated cyclic dienes on single-site catalytic systems of a new generation based on metallocene complexes, “constrained geometry” complexes, and monocyclopentadienyl and post-metallocene chelate IVB-group complexes have been analyzed. The advantages and disadvantages of these catalytic systems have been compared with traditional vanadium catalysts introduced into production in the 1960s and used to date in the industrial synthesis of rubbers. A significant part of the review is devoted to the analysis of patent publications, especially in recent years, belonging to the main world producers of ethylene–propylene–diene rubbers.

Nanofibers of Al2O3 (commercial product Nafen (TM) which were modified by various silane coupling agents have been used to create hybrid materials based on copolymer of ethylene and propylene. Nanocomposites were obtained by in situ catalytic copolymerization on the rac-Et(2-MeInd)(2)ZrMe2/isobutylalumoxane system. Trialkoxysilanes with alkenyl (vinyl and octenyl) and alkyl (octyl) functional groups were used for modification. CP MAS NMR analysis (C-13 and Si-29) of all modified nanoparticles showed the absence of residual alkoxy groups and allowed to identify the type of formed siloxane groups (mainly T-2, T-3). EDX analysis of trimethoxyalkenylsilanes modified nanoparticles showed significant contribution of self-condensation reactions, otherwise, in the case of triethoxyoctylsilane condensation with surface Al-OH groups prevailed. It is found that octylsilane modification leads to remarkable improvement of mechanical properties (tensile strength - approx. 150%, elongation at break - approx. 50% with regard to neat copolymer) at low nanofiller dosage (0.63 wt %), significantly exceeding those for the materials with alkenylsilane treated nanofibers. In the case of octenylsilane even major decline in mechanical performance was observed. We believe that this behavior is determined by the distribution of nanofiller in the polymer matrix, which is markedly different for different surface treatments. TEM observations show that octylsilane modification leads to efficient dispersion of Nafen in polymer matrix, while the use of alkenylsilanes leads to partial or significant aggregation of Nafen particles.

A row of dimeric diisobutylaluminum aryloxides bearing different sterically crowded substituents in ortho-positions of the aryl ligand [(ArO)AllBu(2)](2) (ArO = 2-Bu-t-C-6 H4O (Al-TBP), 2-Me,6-Bu-t-C6H3O (Almmp),2,6-Pr-i(2)-C6H3O (Al-DIpp), 2-Ph-C6H4O (AIpp), 2,6-Ph-2-C6H3O (AI(DPP)), 1-C10H7O (AlN-1)) was synthesized. The Molecular structures of Al-MTBP, AI(DIPP), Al-PP, AI(DPP), and AlN-i have been determined by X-ray crys-tallography. All dimeric diisobutylaluminum aryloxides were tested as activators of rac-Et (2-Melnd)(2)ZrMe2 in homopolymerization of ethylene, propylene, copolymerization of ethylene with propylene and terpolymerization of ethylene/propylene/5-ethylidene-2-norbornene. It was shown that only Al-MTBP and AI(Dpp) work as effective activators in all polymerization processes, with activity of Al-MTBP system being significantly higher than that of AI(DPP). The evaluation of dimerization energies of synthesized aryloxides by means of DFT calculations have shown Al-MTBP and AI(DPP) to form the least stable dimers. The activation ofrac-Et (2-Melnd)(2)ZrMe2 was modeled as bonding of diisobutylaluminum aryloxide with zirconocene followed by the first insertion of ethylene into Zr+-Me bond. As per that model, DFT calculations demonstrated the process to be the most favorable for Al-MTBP and AI(DPP) which well corresponds to experimental observations. (C) 2018 Published by Elsevier B.V.

Nanofibers of Al2O3 (commercial product Nafen (TM)) with characteristic length of similar to 100 nm and diameter of similar to 10 nm were used to create new hybrid materials based on copolymer of ethylene and propylene. Nanocomposites were obtained by in situ catalytic copolymerization on the system rac-Et(2-MeInd)(2)ZrMe2/isobutylalumoxane. Formation of the nanocomposites with uniform distribution of Nafen nanoparticles in polymer matrix was confirmed by scanning and transmission electron microscopy. According to dynamic mechanical analysis data, introduction of the nanofiller in an amount of up to 3 wt % leads to an increase in glass transition temperature by 10 degrees C (E") and by 21 degrees C (tan delta). The nanocomposites exhibit improved physico-mechanical properties (tensile strength and elongation at break). It is shown that the nanofiller significantly improves resistance of the nanocomposite to the thermo-oxidative and thermal degradation. (C) 2016 Wiley Periodicals, Inc.

Isobutylalumoxanes have been obtained by hydrolysis of triisobutylaluminium (TIBA) with water in the form of vapour (1) or ice particles (2) at AlTIBA/H2O = 2 mol/mol. 1H NMR spectra of hydrolyzates showed the presence of unreacted TIBA indicating the formation of alumoxanes larger than i Bu2Al-O-Al i Bu2 which one can expect based on the molar ratio of reagents. Alumoxanes 1 and 2 demonstrate high activating ability for rac-Et(2-MeInd)2ZrMe2 in copolymerization reactions of ethylene with propylene and terpolymerization of ethylene with propylene and 5-ethylidene-2-norbornene. Alumoxane 1 demonstrates high structural and chemical stability during long-term storage (for 1 year) that results in consistent activating ability and similarity of molecular weight characteristics of polymer formed. Alumoxane 2 is much less structurally stable which is manifested in considerable changes of 1H NMR spectra of the product even after several days of storage. It essentially loses activating ability after 3 months’ storage. The alumoxanes with high activating ability have been also obtained by in situ TIBA hydrolysis with water intentionally incorporated into toluene (~1 × 10−2 mol/l) prior to polymerization also at AlTIBA/H2O = 2 mol/mol. The differences of catalytic systems with different activators are also reflected in differences in microstructure, molecular-weight, thermal-physical characteristics and physical-mechanical properties of copolymers formed.

The results of 1H NMR and quantum chemical studies of hydrolysis of isobutylaluminum aryloxides are presented. According to the data of 1H NMR spectroscopy, the hydrolysis of monomeric diisobutylaluminum aryloxides (2,6-Bu2 t—C6H3O)AlBu2 i and (2,6-Bu2 t,4-Me—C6H2O)AlBu2 i occurs selectively at the Al—OAr bond to form the corresponding sterically bulky phenol and polyisobutylaluminoxane. At the molar ratios Al: H2O = 2, the formed sterically bulky phenol reacts slowly with diisobutylaluminum monoaryloxide to form isobutylaluminum diaryloxide. Dimeric aryloxide [(2-But—C6H4O)AlBu2 i]2 is not hydrolyzed under similar conditions. The quantum chemical calculations confirmed the experimental results: the hydrolysis at the Al—OAr bond has a lower energy barrier than that at the Al—C bond because of the formation of \({H_{{H_2}O}} \ldots {O_{O - Ar}}\) hydrogen bonds.

1 H NMR method showed that in systems based on triisobutylaluminum (TIBA) and triphenylcyclopropenylium [Ph 3 C 3 ] + [B(C 6 F 5 ) 4 ]–(CPB) or triphenylmethylium [Ph 3 C] + [B(C 6 F 5 ) 4 ]–(TB) perfluorophenylborates in a toluene–dichloromethane mixture the Friedel–Crafts process occurs with the formation of ditolylmethane (DTM) accompanied by the complete decomposition of TIBA to form isobutane. 19 F NMR spectroscopy showed that the [B(C 6 F 5 ) 4 ]–anion decomposes in the systems to form B(C 6 F 5 ) 3 and HC 6 F 5 . The short-living [AlBu 2 i ]+ cation formed in the reaction of perfluorophenylborates with TIBA is assumed to be the species initiating the process. It has been shown that CPB is less reactive than TB. The addition of a stoichiometric amount of Ph 2 CCpFluHfMe 2 exerts no effect on the process with the CPB-containing system but inhibits the reaction in the case of TB.

ABSTRACTThe article describes that sterically hindered isobutylaluminum aryloxides with bulky tBu substituents at 2,6‐ positions of aryl fragment, i.e. (2,6‐di‐tBu,4‐R‐C6H2O)AliBu2 (R = H (1‐DTBP), Me (1‐BHT), tBu (1‐TTBP)) and (2,6‐di‐tBu,4‐R‐C6H2O)2AliBu (R=H(2‐DTBP), Me(2‐BHT)) can serve as cocatalysts for metallocene complexes. Isobutylaluminum aryloxides have been applied for activation of rac‐Et(2‐MeInd)2ZrMe2 in homopolymerization of ethylene, propylene, copolymerization of ethylene and propylene, and terpolymerization of ethylene, propylene, and 5‐ethylidene‐2‐norbornene at Al/Zr = 300 mol/mol. The type of R substituent at 4‐position has a significant effect on catalyst activity. The catalytic system with 1‐TTBP showed the highest activity in all homo‐ and copolymerization processes. Diisobutylaluminum aryloxides provide much higher activity to the systems in all polymerization processes and stronger ability for propylene incorporation in copolymer than diaryloxides. The activities of the systems with isobutylaluminum aryloxides are similar or exceed that of the system with MAO as activator as have shown for propylene polymerization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43276.

A new method for preparation of zirconium and hafnium phenoxyimine complexes L 2 MCl 2 (L is N -(3,5-di- tert -butylsalicylidene)-2,3,5,6-tetrafluoroanilinate anion, M = Zr, Hf) by the solid state interaction of N -(3,5-di- tert -butylsalicylidene)-2,3,5,6-tetrafluoroaniline, the corresponding metal chlorides, and sodium hydride under mechanical activation followed by heating of the activated mixture was developed. The obtained complexes have a high catalytic activity in the reaction of ethylene polymerization.

A possibility of application of mechanochemical method for the synthesis of triphenylmethylium and triphenylcyclopropenylium tetrakis(pentafluorophenyl)borates by the solvent-free reaction of solid starting compounds was studied. Some specific features of these reactions were discovered. Preparative methods for the mechanochemical synthesis of these salts were developed. This method makes the process shorter and excludes the use of solvents in the synthesis.

Isobutylalumoxanes of different composition were synthesized by the hydrolysis of triisobutylaluminum (TIBA) with crystalline hydrate CuSO 4 ·5H 2 O and water taken as cooled ice or as vapor. The composition of the formed alumoxanes and the degree of water participation in their formation was monitored by 1 H NMR. The hydrolysis of TIBA on CuSO 4 ·5H 2 O is rather selective method of synthesis of alumoxanes. The synthesized alumoxanes were used for the activation of dimethylated zirconocenes rac -Me 2 Si(2-Me,4-PhInd) 2 ZrMe 2 and rac -Et(2-MeInd) 2 ZrMe 2 in propylene polymerization at the molar ratios Al/Zr = 50–750. It was concluded that the hydrolysis afforded several products with different structures and different activating ability. The systems with oligomeric forms of isobutylalumoxanes, especially those obtained by TIBA hydrolysis with water, showed the highest activity.

The transformations of bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]-titanium(iv) dichloride (L2TiCl2) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe3) and MAO free of AlMe3 (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L2TiCl2-MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under the action of AlMe3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe3 to form LAlMe2. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe3 is suppressed. The titanium complex activated by “dry” MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts of TMA (commercial MAO), this reaction does not take place.