Ethene–propene copolymerization with the MgCl2-supported dichlorobis(4,4,4-trifluoro-1-phenyl- 1,3-butanedionato)titanium catalyst activated by an ordinary trialkylaluminum

The Ti(BFA)₂Cl₂/MgCl₂–Al(C₂H₅)₃ catalyst (BFA = 4,4,4-trifluoro-1-phenyl-1,3-butanedione) modified by DIPDMS (diisopropyldimethoxysilane), which had been proved to yield an extremely high isotactic polypropene in high selectivity, was tested for the copolymerization of ethene with propene. The analysis of resulting copolymers by CFC (cross fractionation chromatography) indicated the formation of a small quantity of ethene-rich copolymers as a byproduct, suggesting that the catalyst possesses not only Ti(III) species but a small portion of Ti(II) species. Whereas, the same catalyst without being modified by an external donor selectively yielded propene-rich random copolymers resulting from Ti(III) species in high yields. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2735–2740, 1998     

Highly active MgCl2‐supported catalysts containing novel diether donors for propene polymerization

A new generation of MgCl₂‐supported catalysts for the polymerization of propene without any external donors was prepared. Two diethers, 9,9‐bis(methoxymethyl)fluorene (for Cat‐A) and 2,2‐dipropyl‐1,3‐dimethoxypropane (for Cat‐B) differing in the bulkiness of alkyl substituents in position 2, have been used as internal donors in MgCl₂/TiCl₄/diether‐AlR₃ catalysts. The weight‐average molecular weights produced with both catalysts were over 3.5×10⁵ at low temperature in slurry polymerization (< 40°C). Cat‐A showed higher activity and produced higher isotactic polypropene than Cat‐B. The activity of both catalysts proved to be dependent on the temperature.     

The discovery and progress of MgCl2‐supported TiCl4 catalysts

Polyolefins represented by polyethylene (PE) and polypropylene (PP) are indispensable materials in our daily lives. TiCl₃ catalysts, established by Ziegler and Natta in the 1950s, led to the births of the polyolefin industries. However, the activities and stereospecificities of the TiCl₃ catalysts were so low that steps for removing catalyst residues and low stereoregular PP were needed in the production of PE and PP. Our discovery of MgCl₂‐supported TiCl₄ catalysts led to more than 100 times higher activities and extremely high stereospecificities, which enabled us to dispense with the steps for the removals, meaning the process innovation. Furthermore, they narrowed the molecular weight and composition distributions of PE and PP, enabling us to control the polymer structures precisely and create such new products as very low density PE or heat‐sealable film at low temperature. The typical example of the product innovations by the combination of the high stereospecificity and the narrowed composition distribution is high‐performance impact copolymer used for an automobile bumper that used to be made of metal. These process and product innovations established these polyolefin industries. The latest MgCl₂‐supported TiCl₄ catalyst is very close to perfect control of isotactic PP structure and is expected to bring about further innovations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1–8, 2004     

Living ring‐opening polymerization of ϵ‐caprolactone with Ti alkoxides derived from the Cp2TiCl‐catalyzed SET reduction of aldehydes

A series of substituted benzaldehydes were investigated as initiators for the living ring‐opening polymerization (LROP) of ε‐caprolactone (CL) mediated by titanium alkoxides obtained from the Cp₂TiCl‐catalyzed single electron transfer (SET) reduction of the carbonyl group following the in situ reduction of Cp₂TiCl₂ with Zn. The aldehyde initiation was demonstrated (NMR) by the presence of the initiator derived fragment on the polycaprolactone (PCL) chain end. The effect of the nature of the aldehyde functionality (R‐Ph‐CHO, R = H, Cl, PhCH₂O, NMe₂, CH₃O, NO₂, and CHO), reagent ratios ([CL]/[aldehyde] = 50/1 to 400/1, [aldehyde]/[Cp₂TiCl₂] = 1/1 to 1/4, and [Cp₂TiCl₂]/[Zn] = 1/0.5 to 1/2), and temperature (T = 75–120 °C) was investigated over a wide range of values to reveal a living polymerization in all cases with an optimum observed at 90 °C with typical stoichiometric ratios of [CL]/[aldehyde]/[Cp₂TiCl₂]/[Zn] = 100/1/1/2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2869–2877, 2008     

Cyclopolymerization of 1,5‐hexadiene catalyzed by various stereospecific metallocene compounds

Cyclopolymerization of 1,5‐hexadiene has been carried out at various temperatures in toluene by using three different stereospecific metallocene catalysts—isospecific rac‐(EBI)Zr(NMe₂)₂ [EBI: ethylenebis(1‐indenyl), Cat 1], syndiospecific Me₂C(Cp)(Flu)ZrMe₂ (Cp = 1‐cyclopentadienyl, Flu = 1‐fluorenyl, Cat 2), and aspecific CpZrMe₂ (Cp*: pentamethylcyclopentadienyl, Cat 3) compounds in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]—in order to study the effect of polymerization temperature and catalyst stereospecificity on the property and microstructure of poly(methylene‐1,3‐cyclopentane) (PMCP). The activities of catalysts decrease in the following order: Cat 1 > Cat 2 > Cat 3. PMCPs produced by Cat 1 are not completely soluble in toluene, but those by Cat 2 and Cat 3 are soluble in toluene. trans‐Diisotactic rich PMCPs are produced by Cat 1 and Cat 2, and cis‐atactic PMCP by Cat 3. The cis/trans ratio of PMCP by Cat 1 and Cat 2 is relatively insensitive to the polymerization temperature, but that by Cat 3 is highly sensitive to the polymerization temperature. Melting temperatures of PMCP produced increase with the cis to trans ratio of rings. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1520–1527, 2000     

Manganese‐based transition metal complexes as new catalysts for olefin polymerizations

Three manganese complexes, Mn(acac)₃ (acac = acetylacetonate), Cp₂Mn (Cp = cyclopentadienyl), and Mn(salen)Cl [salen = 1,2‐cyclohexanediamino‐N,N′‐bis(3,5‐dit‐butyl‐salicylidene)], were used for ethylene and propylene polymerizations. These complexes, in combination with an alkylaluminum cocatalyst such as methylaluminoxane (MAO) or diethyl aluminum chloride (AlEt₂Cl), could promote ethylene polymerizations that yielded extremely high molecular weight linear polymers, but were inactive for propylene polymerizations. The counterparts supported on MgCl₂ showed activities even for propylene polymerizations and had remarkably enhanced activities for ethylene polymerizations. In the presence of an electron donor such as ethylbenzoate, the MgCl₂‐supported manganese‐based catalysts yielded a highly isotactic polypropylene with a high molecular weight. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3733–3738, 2001     

Lithium nitride reduction of Cp2TiCl2 and CpTiCl3: The synthesis of (Cp2TiCl2), Cp2TiCl2)n,Cp2Ti(CO)2 and chlorotetratitanium and nitridohexatitanium complexes

Stoichiometric reactions of Cp₂TiCl₂ or CpTiCl₃ with Li₃N in various molar ratios result in reduction to (Cp₂TiCl)₂, (CpTiCl₂)_n and (CpTiCl)₄ and provide useful synthetic routes. Further reduction produces hexanuclear nitrido titanium clusters, Cp₈Ti₆N and Cp₈Ti₆N₃, characterised from mass spectral evidence. The nitrido clusters react with HCl to form (Cp₂TiCl)₂ and Cp₂TiCl₂. (Cp₂TiCl₂ is also obtained by reaction with Me₃SiCl. Cp₂Ti(CO)₂ is formed by the reaction between Cp₂TiCl₂ and Li₃ N in THF in the presence of CO.     

Effect of external donor in polymerization of propylene by a MgCl2 supported titanium catalyst

Polypropylene (PP) prepared with a MgCl₂/TiCl₄-Et₃Al/Ph₂Si(OMe)₂ catalyst system was fractionated by temperature rising elution fractionation method in order to investigate the effect of Ph₂Si(OMe)₂ as an external donor (ED). This PP had a broad and continuous distribution of tacticity. In comparison to the system without donor, however, ED brought a decrease of lower isotactic portions and an increase of higher isotactic ones simultaneously to the resulting polymer. The latter portions were eluted at higher temperature than the corresponding component obtained without donor, showing that the higher isotactic PP was newly produced by ED.     

Copolymerization of ethylene with 1‐hexene over metallocene catalyst supported on complex of magnesium chloride with tetrahydrofuran

The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂)/methylaluminoxane (MAO), anchored on a MgCl₂(THF)₂ support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe₃), or diethylaluminum chloride (Et₂AlCl)] on the behavior of the MgCl₂(THF)₂/Cp₂ZrCl₂/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp₂ZrCl₂ compound on the complex magnesium support MgCl₂(THF)₂ resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004     

Employing (half-)titanocene complexes as initiators for the synthesis of end-functionalized polylactides by coordination polymerization

Seven (half-)titanocene alkoxide complexes, [Cp₂TiCl(OEt)], [Cp₂TiCl(O-2-Bu)], [Cp₂TiCl(OCH₂CF₂CF₂H)], [CpTiCl₂(OEt)], [CpTiCl₂(O-(S)-2-Bu)], [CpTiCl₂(OCH₂CF₃)], and [Cp₂TiCl(OCH₂CF₃)], were synthesized and employed in lactide coordination polymerization. These organotitanium (IV) compounds proved to be very efficient initiators for the ring-opening polymerization of enantiomeric l -lactide and racemic mixture of rac-lactide, leading to end-functionalized polymers. Kinetic studies illustrated that these compounds produce well-defined polymers in a controlled manner. This was further demonstrated by synthesizing poly(l -lactide-b-hexyl isocyanate) diblock copolymer. The effect of the alkoxy end groups on the thermal behavior of the polymers was also studied by thermogravimetric analysis and differential scanning calorimetry. The polymers were characterized using size exclusion chromatography and proton nuclear magnetic resonance spectroscopy. The optical properties of the diblock copolymer were also investigated. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2192–2202     

Polymerization of propylene with the [ArN(CH2)3NAr]TiCl2 (Ar = 2,6-iPr2C6H3) complex using R3Al/Ph3CB(C6F5)4 (R = Me,Et, iBu) as cocatalyst

Polymerization of propylene was conducted at 0 ∼ 150°C with the [ArN(CH₂)₃NAr]TiCl₂ (Ar = 2,6-ⁱPr₂C₆H₃) complex using a mixture of trialkylaluminium (AIR₃, R = methyl, ethyl and isobutyl) and Ph₃CB(C₆F₅₎₄ as cocatalyst. When AlMe₃ or AlEt₃ was employed, atactic polypropylene (PP) was selectively produced, whereas the use of Al(ⁱBu)₃ gave a mixture of atactic and isotactic PP. The isotactic index (I.I.; weight fraction of isotactic polymer) depended strongly upon the polymerization temperature, and the highest I.I. was obtained at ca. 40°C. The ¹³C NMR analysis of the isotactic polymer suggests that the isotactic polymerization proceeds by an enantiomorphic-site mechanism. It was also demonstrated that the present catalyst shows a very high regiospecificity.     

Polymerization of methyl methacrylate using a metallocene catalyst system

Methyl methacrylate was polymerized with Cp₂YCl(THF) or IVB group metallocene compounds (i.e., Cp₂ZrCl₂ and Cp₂HfCl₂, etc.), in the presence of a Lewis acid like Zn(C₂H₅)₂. The Lewis acid was complexed with methyl methacrylate, which avoided the metallocene compounds being poisoned with a functional group. A living polymerization was promoted through the use of metallocene/MAO/Zn(C₂H₅)₂, which gave tactic poly(methyl methacrylate) with a high molecular weight. The polymer yield increases with polymerization time, which indicates that the propagation rate is zero in order in the concentration of the monomer. The polymer yield increases also with the concentration of Cp₂YCl(THF), which indicates the yttrocene to be the real catalyst. When the polymerization temperature exceeds room temperature, the poly(methyl methacrylate) cannot be synthesized by the Cp₂YCl(THF) catalyst. When the reaction temperature reachs −60 °C, the poly(methyl methacrylate) is high syndiotatic and molecular weight by the Cp₂YCl(THF)/MAO catalyst system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1184–1194, 2000     

Silanolato-Komplexe von Titan und Zirconium. Die Kristallstrukturen von Cp2TiCl(OSiPh3) und Cp2ZrCl(OSiPh3)

Silanolato Complexes of Titanium and Zirconium. The Crystal Structures of Cp₂TiCl(OSiPh₃) and Cp₂ZrCl(OSiPh₃) The title compounds have been prepared by the reaction of Cp₂MCl₂ (M = Ti, Zr) with triphenylsilanole in diethylether in the presence of piperidine. They form only sparingly moisture sensitive orange (Ti) or colourless (Zr) crystal needles, which were characterized by X-ray crystallography. Cp₂TiCl(OSiPh₃): Space group P2₁/n, Z = 4, structure solution with 3961 observed unique reflections, R = 0.057. Lattice dimensions at 20°C: a = 1029.6, b = 1719.3, c = 1388.9 pm, β = 100.69°. The compound forms monomeric molecules with bond lengths TiO of 184.2 pm, SiO of 161.5 pm, and a TiOSi bonding angle of 164.5°. Cp₂ZrCl(OSiPh₃): Space group P3 , Z = 18, structure solution with 2799 observed unique reflections, R = 0.047. Lattice dimensions at ?20°C: a = b = 3518, c = 1058.3 pm. The structure consists of three symmetry-independent monomeric molecules, which differ only slightly. The bond lengths are (in average): ZrO 196.4 pm, SiO 162.1 pm, the ZrOSi bond angle is 173.7°.     

Synthesis of polypropylene graft copolymers by the combination of a polypropylene copolymer containing pendant vinylbenzene groups and atom transfer radical polymerization

This article discusses a facile and inexpensive reaction process for preparing polypropylene‐based graft copolymers containing an isotactic polypropylene (i‐PP) main chain and several functional polymer side chains. The chemistry involves an i‐PP polymer precursor containing several pendant vinylbenzene groups, which is prepared through the Ziegler–Natta copolymerization of propylene and 1,4‐divinylbenzene mediated by an isospecific MgCl₂‐supported TiCl₄ catalyst. The selective monoenchainment of 1,4‐divinylbenzene comonomers results in pendant vinylbenzene groups quantitatively transformed into benzyl halides by hydrochlorination. In the presence of CuCl/pentamethyldiethylenetriamine, the in situ formed, multifunctional, polymeric atom transfer radical polymerization initiators carry out graft‐from polymerization through controlled radical polymerization. Some i‐PP‐based graft copolymers, including poly(propylene‐g‐methyl methacrylate) and poly(propylene‐g‐styrene), have been prepared with controlled compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 429–437, 2005     

Synthesis and characterization of some bis(cyclopentadienyl)titanium(IV) complexes with internally functionalized oximes(LH): sol–gel transformations of Cp2TiCl2, Cp2TiClL and Cp2TiL2 to nano‐sized anatase titania

Some bis(cyclopentadienyl)titanium(IV) complexes of the type [Cp₂TiCl_2?n{L}_n] {where, n = 1 or 2; L = ONC(R)Ar; R = H or CH₃ and Ar = C₅H₄N‐2, C₄H₃O‐2 or C₄H₃S‐2} have been synthesized by the metathetical reactions of Cp₂TiCl₂ with the sodium salt of internally functionalized oximes in 1:1 and 1:2 stoichiometry in anhydrous THF. All these red to brown colored solid derivatives have been characterized by elemental analyses, FT‐IR and NMR (¹H and ¹³C{¹H}) spectral studies. The FAB mass spectra of some representative derivatives indicate their monomeric nature. Oximato ligands in all the complexes appear to bind the titanium via N and O in a dihapto ( ‐N, O) manner in the solid state. Thermogravimetric curves of [Cp₂TiCl{ONC(CH₃)C₅H₄N‐2}] and [Cp₂Ti{ONC(CH₃)C₅H₄N‐2}₂] suggest the formation of hybrid materials CpTiO(Cl) and Cp₂TiO, respectively, as the final products at 900 °C under nitrogen atmosphere. Sol–gel transformations of Cp₂TiCl₂, [Cp₂TiCl{ONC(CH₃)C₅H₄N‐2}] and [Cp₂Ti{ONC(CH₃)C₅H₄N‐2}₂] yielded titania a–c, respectively, at low sintering temperature (600 °C). The powder XRD patterns, IR as well as Raman spectra of all these oxides indicate the formation of nano‐sized anatase phase. The SEM images of titania a–c indicate agglomers like surface morphologies. The absorption spectra of a–c exhibit an energy band gap in the range of 3.47–3.71 eV. Copyright © 2011 John Wiley & Sons, Ltd.     

Polydentate phosphine oxides as external electron donors for titanium-magnesium catalysts for propylene polymerization

The possibility of using R _n P(O)(CH₂OR′)_3—n (R = alkyl, R′ = methyl or acyl, n = 0–2) polydentate phosphine oxides as external electron donors for the titanium-magnesium catalysts for isotactic polypropylene synthesis is demonstrated for the first time. The kinetics of propylene polymerization in liquid monomer at 70°C and the isotacticity and molecular-weight characteristics of the resulting polypropylene are studied as functions of the nature of the substituents at the phosphorus atoms in the external donor and the molar ratio of the cocatalyst AlEt₃ to the external electron donor. Among the compounds examined, isoamyldi(methoxymethyl)phosphine oxide (R = iso-Am, R′ = Me, n = 1) is the most efficient. The isotacticity index of the polypropylene (PP) synthesized on the titanium-magnesium catalyst with this external donor is as high as 94–95%, and the activity of the catalyst (Cat) in the absence of hydrogen is 5.0–6.5 (kg PP) (g Cat)^?1 h^?1. With the optimum combination, the activity of this catalyst is ≈5 (kg PP) (g Cat)^?1 h^?1 and the isotacticity index is 94%. These parameters are close to those obtained for propylene polymerization in the absence of hydrogen on the same titanium-magnesium catalyst with phenyltriethoxysilane (external donor used in the industrial synthesis of PP): the activity is 5.6 (kg PP) (g Cat)^?1 h^?1, and the isotacticity index is 95%. The introduction of hydrogen into the reaction zone makes it possible to efficiently control the molecular weight of PP, increases the catalyst activity by a factor of 1.5–2.5, and somewhat decreases the isotacticity index (from 94 to 91–92%).     

Free radical-promoted conjugate addition of activated bromo compounds using titanocene(III) chloride as the radical initiator

Free radical-promoted conjugate addition of activated bromo compounds to α,β-unsaturated ketones and reactive α,β-unsaturated esters has been described using titanocene(III) chloride (Cp₂TiCl) as the radical initiator. Cp₂TiCl was prepared in situ from commercially available Cp₂TiCl₂ and activated zinc dust in THF.     

Propene polymerization with the MgCl2-supported dichlorobis(β-diketonato)titanium catalysts activated by ordinary alkylaluminums

Several kinds of dichlorobis(β-diketonato)titanium complexes, i.e., Ti(ace-tylacetonato)₂Cl₂, Ti(1-benzoylacetonato)₂Cl₂, Ti(2,2,6,6-tetramethyl-3,5-heptanedionato)₂Cl₂ and Ti(4,4,4-trifluoro-1-phenyl-1,3-butanedionato)₂Cl₂, were synthesized and the corresponding MgCl₂-supported catalysts were prepared by impregnation method. The test of them for propene polymerization revealed that those MgCl₂-supported catalysts could be activated not only by methylaluminoxane (MAO) but also by ordinary alkylaluminums as well. The effect of typical Lewis bases on the catalyst performance was investigated in some detail, which indicated that organic silanes are most effective for the improvement of isospecificity of those catalysts. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 129–135, 1998     

Radical-mediated synthesis of 3,4-dihydroisocoumarins: total synthesis of hydrangenol

A radically promoted synthesis of 3,4-dihydroisocoumarins has been achieved in moderate to good yields using titanocene(III) chloride (Cp₂TiCl) as the radical initiator. The total synthesis of (±)-hydrangenol has been completed using this radical technology. Cp₂TiCl was prepared in situ from commercially available titanocene dichloride (Cp₂TiCl₂) and Zn-dust in THF under argon.     

Similarities and differences of epoxide, aldehyde and peroxide initiators for Cp2TiCl-catalyzed styrene living radical polymerizations

Cp₂TiCl is the first example of a single electron transfer (SET) agent that both provides initiating radicals from three different types of functionalities (i.e. radical ring opening of epoxides and reduction of aldehydes and peroxides) and doubles as mediator for the living radical polymerization of styrene (St) by reversibly endcapping the growing polymer chains. An initiator (I) comparison was performed using 1,4-butanediol diglycidyl ether (BDE), benzaldehyde (BA) and benzoyl peroxide (BPO) as models. The investigation of the effect of reaction variables was carried out over a wide range of experimental conditions ([Cp₂TiCl₂]/[I] = 0.5/1-4/1; [Zn]/[Cp₂TiCl₂] = 0.5/1-3/1, [St]/[I] = 50/1-400/1 and T = 60-130 °C) to reveal living polymerization features such as a linear dependence of molecular weight on conversion and narrow molecular weight distribution (M_w/M_n) for each initiator class. However, progressively lower polydispersities and larger initiator efficiencies are obtained with increasing the [Cp₂TiCl₂]/[I] and [Zn]/[Cp₂TiCl₂] ratios and with decreasing temperature. Accordingly, optimum conditions correspond to [St]/[I]/[Cp₂TiCl₂]/[Zn] = [50-200]/[1]/[2-3]/[4-6] at 70-90 °C. By contrast to peroxides, aldehydes and the more reactive epoxides provide alcohol end groups useful in block or graft copolymers synthesis.