Homogeneous Ziegler-Natta Catalysts Research Articles

Transition metal-catalyzed polymerization of polar allyl and diallyl monomers

Abstract

(“Ferrocene-salaldiminato”)zirconium Complexes for Ethylene Polymerization Catalysis: The Role of the Bulky Substituents

We prepared the 2-hydroxy-5-trimethylsilylferrocenecarbaldimine systems 13 enantioselectively by a short synthetic route starting from the chiral ferrocene carbaldehyde acetal 5. The imines 13a–c were used to synthesize the zwitterionic (“ferrocene-salaldiminato”)2ZrCl4 complexes 14a–c. Activation with MAO gave homogeneous Ziegler–Natta catalysts, which showed only a moderate ethylene polymerization activity, similar to the unsubstituted parent “ferrocene-salaldiminato” zirconium systems. Consequently, a synthetic route was devised and carried out to make the corresponding 2-hydroxy-3,5-bis(trimethylsilyl)ferrocenecarbaldimines (21) available. The enantiomerically highly enriched ligands (pS)-21a and -d derived from the aldehyde and aniline or cyclohexylamine, respectively, were used to synthesize the corresponding (“ferrocene-salaldiminato”)2ZrCl4 complexes 22a,d. Both gave highly active homogeneous Ziegler–Natta catalysts upon activation with MAO for the formation of linear low molecular weight polyethylene. Complex 22d and many ligand precusors from both sequences were characterized by X-ray diffraction.

Synthesis of [3]ferrocenophane-bridged Cp–amido zirconium complexes and ansa-zirconocene complexes and their use in catalytic polymerisation reactions

Starting from 1,1'-diacetylferrocene the ortho-amino,α-dimethylamino[3]ferrocenophane system 3 was prepared. This was converted to the o-imino,α-Cp-derivative 6. Subsequent treatment with e.g. an excess of methyllithium followed by ZrCl(2)(NMe(2))(2)(thf)(2) and Me(2)SiCl(2) eventually gave the [3]ferrocenophane based Cp-amido zirconium complex 11b. In a similar way the [3]ferrocenophane derived fluorenyl-Cp ansa-zirconocene dichloride complex 20 was obtained. The 20-methylalumoxane (MAO) system is an active homogeneous Ziegler-Natta catalyst for ethylene polymerization. The 11b-MAO system reacts efficiently with an ethene-1-octene mixture to yield a mixture of linear polyethylene plus the ethene-1-octene copolymer. The compounds 5, 8, 10b, 11b, 13, 14, and 20 were characterized by X-ray diffraction.

Highly cis-1,4 Selective Polymerization of Dienes with Homogeneous Ziegler−Natta Catalysts Based on NCN-Pincer Rare Earth Metal Dichloride Precursors

The first aryldiimine NCN-pincer ligated rare earth metal dichlorides (2,6-(2,6-C6H3R2N=CH)2-C6H3)LnCl2(THF)2 (Ln = Y, R = Me (1), Et (2), iPr (3); R = Et, Ln = La (4), Nd (5), Gd (6), Sm (7), Eu (8), Tb (9), Dy (10), Ho (11), Yb (12), Lu (13)) were successfully synthesized via transmetalation between 2,6-(2,6-C6H3-R2N=CH)2-C6H3Li and LnCl3(THF)(1-3.5). These complexes are isostructural monomers with two coordinating THF molecules, where the pincer ligand coordinates to the central metal ion in a kappaC:kappaN:kappaN' tridentate mode, adopting a meridional geometry. Complexes 1-6, 9-11, and 13 combined with aluminum tris(alkyl)s and [Ph3C][B(C6F5)4] established a homogeneous Ziegler-Natta catalyst system, which exhibited high activities and excellent cis-1,4 selectivities for the polymerizations of butadiene (T(p) = 25 degrees C, 99.9%; 0 degrees C, 100%) and isoprene (T(p) = 25 degrees C, 98.8%). Remarkably, such high cis-1,4 selectivity almost remained at elevated polymerization temperatures up to 80 degrees C and did not vary with the type of the central lanthanide element, however, which was influenced obviously by the ortho substituent of the N-aryl ring of the ligands and the bulkiness of the aluminum alkyls. The Ln-Al bimetallic cations were considered as the active species. These results shed new light on improving the catalytic performance of the conventional Ziegler-Natta catalysts for the specific selective polymerization of dienes.

Functional Elastomers via Sequential Selective Diene Copolymerization/Hydrophosphorylation Catalysis

AbstractAn effective preparation of new tailor‐made macromolecular materials via the combination of two fully atom‐efficient catalytic transformations is reported. First, new isoprene‐co‐1,3,7‐octatriene [P(IP‐co‐OT)] copolymers with controlled composition (2–21 mol% triene incorporated), molecular weight (Mn=23–102,000 g mol−1) and microstructure (1,4‐cis rich) have been prepared using the homogeneous Ziegler–Natta catalyst system composed of diallylneodynium chloride, magnesium chloride, tetrahydrofuran and methylaluminoxane [Nd(allyl)2Cl(MgCl2)2(THF)4/MAO]. Next, the pendant vinyl moieties in those P(IP‐co‐OT) copolymers have been selectively transformed into phosphonate groups by hydrophosphorylation in the presence of homogeneous rhodium phosphine catalysts. The latter hydrophosphorylation reaction has been optimized in terms of catalytic activity and selectivity, to define the conditions for an effective and safe procedure that does not affect the macromolecular architecture. All polymer materials have been microstructurally analyzed by 1H, 13C, and 31P NMR spectroscopy, to diagnose the catalyst selectivities in the copolymerization and hydrophosphorylation processes.

Low Cis Polymerization of Butadiene Using TiCl4 and Bisupported with SiO2/MgCl2(Ethoxide Type)/TiCl4 Catalysts

Abstract To obtain low cis polymer of butadiene (PBR), heterogenous and homogeneous Ziegler-Natta catalyst of TiCl4 were used. SiO2 and Mg(OEt)2 were used as supports for the heterogenous catalyst, while TiCl2 was used as a soluble catalyst. Triisobutylaluminium (TIBA) was used as a cocatalyst. Optimum molar ratio of Al/Ti = 1.5 : 1 and Al:Ti = 13 : 1 were obtained for TiCl4/TIBA and SiO2/MgCl2 (ethoxide type)/TiCl4/TIBA catalyst systems, respectively, regarding productivity of the catalysts. Effect of the temperature of 25–65 °C on polymerization was studied for the bisupport one; while for the TiCl4 temperature control was difficult. This could be due to the obtained high gel content of polymer. The highest yield of PBR was obtained at 55 °C using the bisupported catalyst. Addition of H2 as a chain transfer agent decreased cis%, gel content and the yield of polymer obtained. Increasing polymerization temperature when H2 was used was negligible, which had an affect on the gel content of the polymer. Productivity of the bisupported catalyst was higher than the TiCl4 catalyst itself and the polymerization temperature was under control as well. Polymer with cis content of 4 to 65% was obtained using different catalyst and different polymerization conditions.

Formation of a butadienenickel-based zwitterionic single-component catalyst for ethylene polymerization: an alternative activation pathway for homogeneous Ziegler-Natta catalysts of late transition metals.

Addition of B(C6F5)3 to the butadiene ligand in 1 leads to the zwitterionic complex 2 (characterized by single-crystal X-ray diffraction; Ar=2,6-diisopropylphenyl), which is an active catalyst for the polymerization of ethylene. The formation of 2 could have model character for an activation pathway for homogeneous Ziegler–Natta catalysts of late transition metals without σ-alkyl ligands.

Formation of cyclodimeric (sp(2)-C(1))-bridged Cp/-oxido ("CpC(1)O"M(IV)X(2)) group 4 metal Ziegler-Natta catalyst systems--how important is the "constrained geometry" effect?

Deprotonation of sodium acetylcyclopentadienide (11) was achieved by treatment with LDA in THF to generate the dianion equivalent [Cp-C(=CH(2))-O](2-)(12). Transmetalation with Cl(2)Ti(NMe(2))(2) gave ([Cp-C(=CH(2))-O]Ti(NMe(2))(2))(2) (17); treatment of 12 with Cl(2)Zr(NEt(2))(2)(THF)(2) furnished (([Cp-C(=CH(2))-O]Zr(NEt(2))(2))(2) (18). Cryoscopy in benzene revealed a dimeric structure of 18 in solution. Complex 18 was characterized further by an X-ray crystal structure analysis and by DFT calculations. The two zirconium centers of 18 are connected by means of two symmetry-equivalent eta(5):kappaO[Cp-C(=CH(2))-O] ligands. The ligand backbone shows no specific steric constraints, different from the formally related "constrained geometry" systems such as [Cp-SiMe(2)-NCMe(3)]Zr(NMe(2))(2) (1b). Nevertheless, upon treatment with MAO the CpCO group 4 metal complex system (18) generates an active homogeneous Ziegler-Natta catalyst for effective ethene/1-octene copolymerization, with up to 20% 1-octene having become incorporated in the resulting copolymer at 90 degrees C.

Electronic effects in homogeneous Ziegler–Natta catalysts: Zr–Rh early–late heterobimetallic complexes †

Download options Please wait... Supplementary files Crystal structure data TXT (96K) Article information DOI https://doi.org/10.1039/B008491N Article type Paper Submitted 20 Oct 2000 Accepted 31 Jan 2001 First published 26 Feb 2001 Download Citation J. Chem. Soc., Dalton Trans., 2001, 948-953 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Electronic effects in homogeneous Ziegler–Natta catalysts: Zr–Rh early–late heterobimetallic complexes C. Takayama, Y. Yamaguchi, T. Mise and N. Suzuki, J. Chem. Soc., Dalton Trans., 2001, 948 DOI: 10.1039/B008491N To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Chikako Takayama Yoshitaka Yamaguchi Takaya Mise Noriyuki Suzuki

Triazamethylenemethane complexes of zirconium and tantalum

Addition of [Li 2(THF) 4][C(NPh) 3] ( 2) to a THF solution of Cp *ZrCl 3 (Cp *=C 5Me 5) yields, after recrystallization in Et 2O, the zwitterionic species Cp *[C(NPh) 3]ZrCl 2Li(Et 2O)(THF) ( 3). Treating 3 with excess methylaluminoxane (MAO) affords a homogeneous Ziegler–Natta catalyst for ethylene polymerization. Addition of LiNPh 2 to 3 allows for Cl substitution to give the new product Cp *[C(NPh) 3]Zr(NPh 2)ClLi(THF) 2 ( 4). A single crystal diffraction study of 4 reveals that the [C(NPh) 3] ligand is η 2-bound. The group 5 complex Cp *[C(NPh) 3]TaMe 2 ( 5) was prepared by addition of 2 to Cp *TaMe 2Cl(OSO 3CF 3). The X-ray diffraction structure of 5 shows that the [C(NPh) 3] ligand is η 2-bound to tantalum and that, when compared to 4, there is less electron delocalization across the inner core of [C(NPh) 3].

Synthesis and characterization of highly conducting polyacetylene

Polyacetylene can be synthesized by several routes. Among them, the most widely used method is an interfacial polymerization of acetylene monomer on a surface of a concentrated homogeneous Ziegler-Natta catalyst solution. The product is obtained as a form of thin films, which are served as specimens for characterization and measurements of various properties. The quality of the films is dependent strongly on preparative method of the catalyst as well as the polymerization condition of acetylene because there is no way to process the film due to its insolubility and infusibility. Synthetic conditions of highly conducting polyacetylene films and their characterization are reviewed in terms of catalyst preparations and polymerization methods.

Deconvolution of chain-length distributions of linear polymers made by multiple-site-type catalysts

Polyolefins made using most heterogeneous and some homogeneous Ziegler—Natta catalysts show a characteristic broad molecular-weight distribution, generally assumed to be caused by the presence of more than one active site type, each type producing polymer with an instantaneous chain-length distribution that is most probable and having polydispersity of 2. Herein is reported a comparison of two numerical methods for the deconvolution of instantaneous chain-length distribution of linear homo- and copolymers made using multiple-site-type catalysts giving an individual most probable chain-length distribution for each site type, and a methodology is proposed for the efficient deconvolution of measured chain-length distributions.

Effects of Regiochemical and Stereochemical Errors on the Course of Isotactic Propene Polyinsertion Promoted by Homogeneous Ziegler-Natta Catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of Regiochemical and Stereochemical Errors on the Course of Isotactic Propene Polyinsertion Promoted by Homogeneous Ziegler-Natta CatalystsVincenzo Busico, Roberta Cipullo, John C. Chadwick, Johan F. Modder, and Olof SudmeijerCite this: Macromolecules 1994, 27, 26, 7538–7543Publication Date (Print):December 1, 1994Publication History Published online1 May 2002Published inissue 1 December 1994https://doi.org/10.1021/ma00104a006RIGHTS & PERMISSIONSArticle Views501Altmetric-Citations129LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (590 KB) Get e-Alerts Get e-Alerts

Enantioselectivity in the Regioirregular Placements and Regiospecificity in the Isospecific Polymerization of Propene with Homogeneous Ziegler-Natta Catalysts

Enantioselectivity in the Regioirregular Placements and Regiospecificity in the Isospecific Polymerization of Propene with Homogeneous Ziegler-Natta Catalysts

Novel polypropene materials derived from vinylidene‐terminated oligopropenes

AbstractMetallocene‐based homogeneous Ziegler–Natta catalysts produce mono‐olefin‐terminated oligopropenes with narrow molecular weight distributions, controlled stereoregularities, and molecular weights ranging from 100 to 30,000 g/mole in high yield slurry and solution processes. Steric and molecular weight control are influenced by metallocene structures, and by polymerization conditions such as temperature and propene concentration. Predominantly mono‐vinylidene‐terminated oligopropenes are attractive intermediates, and feedstock for the synthesis of a variety of polypropylene materials, including blends, block and graft copolymers. The key step is the chain end functionalization of the vinylideneterminated oligopropenes via double bond conversion reactions, followed by the controlled synthesis of polypropylene block and graft copolymers. In melt and solution processes the olefinic end groups have been converted into a variety of polar functional groups, e.g. hydroxy, carboxy, succinic anhydride, thiol and acrylic groups. The thiol‐terminated oligopropenes are chain transfer agents in radical methylmethacrylate polymerization with chain transfer constant measured to be 0.2. Acrylic monomers and styrene are grown onto the thiol end group via a chain transfer reaction, thus producing a family of block copolymers, e.g. poly(propene‐b‐methylmethacrylate) and poly(propene‐b‐styrene). As demonstrated by SEM fracture surface analysis, the poly(propene‐b‐styrene) block copolymers are efficient dispersing agents for compatibilizing polystyrene/polypropene (70/30) blends. Homo‐ and copolymerization of acrylic oligopropene macromonomers yield novel classes of graft copolymers with pendant isotactic or atactic oligopropene chains. Hydroxy‐terminated oligopropenes are useful initiators in caprolactone polymerization to form poly(propene‐b‐caprolactone) block copolymers. IR spectroscopic studies demonstrate that succinic anhydride‐terminated oligopropenes, obtained by ene‐type addition of maleic anhydride to the olefinic oligopropene end group, react with oligomeric diamine‐terminated polyamide‐6,6 in the melt to yield polypropene‐b‐polyamide‐6,6‐b‐polypropene triblock copolymers.

Ethylene–hexene copolymerization by heterogeneous and homogeneous Ziegler–Natta catalysts and the “comonomer” effect

AbstractHomopolymerization of ethylene and 1‐hexene and their copolymerizations were compared to investigate the influence of α‐olefin on the enhancement of ethylene polymerization rate (Rp), which is often referred to as the “comonomer” effect. With the two homogeneous Ziegler–Natta catalysts, Et[Ind]2ZrCl2/MAO and (π‐C5H5)2ZrCl2/MAO (MAO = methylaluminoxane), hexene causes reduction of Rp—in other words a negative “comonomer” effect. In the case of the high activity MgCl2 supported TiCl3 catalysts there is a slight positive “comonomer” effect; the Rp increases by 25 to 70% with the addition of 15 mol % of hexene. The “comonomer” effects in there catalyst systems are much smaller than that observed for the classical TiCl3 catalyst. © 1993 John Wiley & Sons, Inc.

The microstructure of poly(cyclopentene) produced by polymerization of cyclopentene with homogeneous Ziegler-Natta catalysts

The hydro-oligomerization of cyclopentene in toluene solution using [ethylenebis(η 5 -indenyl)]-zirconium dichloride (1) or bis(cyclopentadienyl)zirconium dichloride and methylaluminoxane as catalysts was studied. The results conclusively demonstrate that the original structure assigned to poly(cyclopentene) is incorrect and that enchainment of cyclopentene occurs predominantlt by cis-1,3-insertion. A mechanism for the polymerization of cyclopentene using catalyst 1 is discussed.

Stereospecific Cyclopolymerization with Group 4 Metallocenes

Abstract Homogeneous Ziegler-Natta catalysts are stereoselective cyclopolymerization catalysts for non-conjugated dienes. Cyclopolymerization of 1,5-hexadiene affords poly(methylene-l,3-cyclopentane) (PMCP), a polymer for which four structures of maximum order are possible. A variety of metallocene catalyst precursors have been investigated; the molecular weight and microstructure of the polymers are sensitive to the structure of the catalyst precursor as well as the reaction conditions. The selectivity for cyclization depends on reaction conditions; decreasing the olefin concentration and increasing the temperature of the reaction favor cyclization. The stereochemistry of cyclopolymers can also be controlled with appropriate choice of catalyst precursor. Diastereoselective cyclopolymerization of 1,5-hexadiene with achiral catalysts yields atactic trans-PMCP and cis-PMCP, depending on the catalyst precursor. Enantioselective cyclopolymerization with optically active catalysts yields optically active poly(...

Polymerization of butadiene in polystyrene with a homogeneous Ziegler-Natta catalyst

Polymerization of butadiene in polystyrene with a homogeneous Ziegler-Natta catalyst

Polymerization of olefins with homogeneous zirconocene/alumoxane catalysts

Abstract The homogeneous Ziegler-Natta catalyst, consisting of zirconocene compounds and methylalumoxane, leads to extremely high polymerization activities. With bis(cyclopentadienyl) zirconium dichloride, polyethylene with activities up to 40 x 106 g PE/g Zr·h is formed. The higher the degree of oligomerization of the alumoxane the more active are the catalysts. The density of polyethylene (LLDPE) can be lowered by using 1-butene or 1- hexene as comonomers. Incorporation of dienes gives EPDM-elastomers. Highly isotactic polypropylene can be prepared by using chiral rac-ethylene bis(tetrahydroindenyl) zirconium dichloride together with methylalumoxane as cocatalyst. The toluene soluble part here consists of less than 0.2 weight per cent. Cyclopentene gives a highly isotactic and insoluble polymer. With the R or S enantiomers of the catalyst it is also possible to produce optically active oligomers. The side reactions and the mechanism are discussed.