A cationic bridged zirconocene complex as the catalyst for the stereospecific polymerization of methyl methacrylate

Stuhldreier, Thomas; Keul, Helmut; Höcker, Hartwig

doi:10.1002/1521-3927(20001001)21:15<1093::aid-marc1093>3.0.co;2-5

Cited by 31 publications

(38 citation statements)

References 13 publications

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“…The synthesis of isotactic PMMA was enabled by introduction of a chiral initiator through an enantiomorphic site‐control mechanism . Further investigations on single component cationic zirconocene complexes uncovered that isotactic as well as syndiotactic PMMA are accessible depending on the symmetry of the catalyst . Although MMA polymerization with [Me 2 CCpIndZrMe(THF)][BPh 4 ] is highly isospecific at room temperature, symmetric [Me 2 CCp 2 ZrMe(THF)][BPh 4 ] leads to syndiotactic PMMA at low temperatures …”

Section: Catalysts In Group‐transfer Polymerizationmentioning

confidence: 99%

“…[11g] catalyst. [3,19] Although MMA polymerization with [Me 2 CCpIndZrMe(THF)][BPh 4 ]i sh ighly isospecific at room temperature, symmetric [Me 2 CCp 2 ZrMe(THF)][BPh 4 ]leads to syndiotactic PMMA atl ow temperatures. [3] The scope of accessible monomers for zirconocene-mediated GTP was broadened in 2004 by Mariott and Chen.…”

Section: Catalysts In Group-transfer Polymerizationmentioning

confidence: 99%

See 1 more Smart Citation

Metal‐Catalyzed Group‐Transfer Polymerization: A Versatile Tool for Tailor‐Made Functional (Co)Polymers

Adams

Pahl

Rieger

2017

Chemistry A European J

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Accommodating the increasing demand for tailor-made polymers is a major goal in polymer chemistry. Therefore, the investigation of polymerization techniques, which allow the precise synthesis of macromolecules is of exceptional interest. Ionic or controlled radical polymerization are capable living-type methods for the generation of uniform polymers. However, even these approaches reach their limits in certain issues. In the last decades, group-transfer polymerization (GTP) and especially metal-catalyzed GTP have proven to give access to a plethora of tailor-made homo- and copolymers based on α,β-unsaturated monomers. Thereby, GTP has established its potential in the development of functional and smart polymers. This concept article highlights the most significant progress in metal-catalyzed GTP with a focus on functional (co)polymers including different polymeric architectures and microstructures.

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Section: Catalysts In Group‐transfer Polymerizationmentioning

confidence: 99%

Section: Catalysts In Group-transfer Polymerizationmentioning

confidence: 99%

Metal‐Catalyzed Group‐Transfer Polymerization: A Versatile Tool for Tailor‐Made Functional (Co)Polymers

Adams

Pahl

Rieger

2017

Chemistry A European J

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“…We were the first to show that [Zr{(Cp)(Ind)CMe 2 }(Me)(thf)](BPh 4 ) (Ind indenyl, Cp cyclopentadienyl) is a stereoselective one-component catalyst that polymerises MMA selectively to isotactic poly(methyl methacrylate) (PMMA) with no additional cocatalysts or activators. [4] Since no theoretical investigations on stereoselective polymerisations of MMA with C 1 -symmetric zirconocenes have been reported, we investigated our catalyst system by means of Hartree ± Fock calculations in an effort to gain a better insight into the mechanism of the polymerisation.…”

Section: Introductionmentioning

confidence: 99%

“…This bound MMA molecule then reacts with the enolate moiety bound to the zirconium centre. Since our experimental work [4,6] has shown that the single-component catalyst [Zr{(Cp)(Ind)CMe 2 }(Me)(thf)](BPh 4 ) yields highly isotactic PMMA very efficiently, whereas syndiotactic PMMA is obtained with [Zr{(Cp) 2 CMe 2 }(Me)(thf)](BPh 4 ), [6] we studied the influence of the indenyl system on the reaction Scheme 1. Initial steps of the polymerisation of MMA with singlecomponent cationic zirconocenes of the form [Zr(LL')(Me)(MMA)] (in this work LL' (Cp)(Ind)CMe 2 ).…”

Section: Introductionmentioning

confidence: 99%

Postulation of the Mechanism of the Selective Synthesis of Isotactic Poly(methyl methacrylate) Catalysed by [Zr{(Cp)(Ind)CMe2}(Me)(thf)](BPh4): A Hartree-Fock, MP2 and Density Functional Study

2001

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The bridged. C1-symmetric, single-component zirconocene [Zr((Cp)(Ind)CMe2](Me)(thf)](BPh4) (Ind = indenyl, Cp = cyclopentadienyl) polymerises methyl methacrylate (MMA) selectively to isotactic poly(methyl methacrylate) (PMMA) without further cocatalysts or activators. To elucidate the stereoselective steps of the polymerisation of MMA by using this catalyst we studied the propagation steps occurring with the derivative [Zr[(Cp)(Ind)CH2][-O-C(OMe)=C(Me)(Et)](MMA)]+ by ab initio calculations at the Hartree-Fock(HF) level of theory. After the initiation step, which consumes the first two MMA molecules, each new catalytic cycle begins with the stereoselective addition of a new MMA molecule at the indenyl side of the zirconocene fragment. At the same time the enolate ring undergoes a stereoselective in-plane ring shift to the side opposite to the indenyl ring. These findings are used to postulate a mechanism for the polymerisation that explains the stereoselective synthesis of isotactic PMMA.

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“…Zirconocene cations were produced in situ by treating Cp 2 ZrMe 2 with an equimolar amount of B(C 6 F 5 ) 3 , and a nearly complete conversion of MMA without a co-initiator was observed. Analogous systems were investigated by Höcker et al [11,12] THF-stabilized zirconocene cations were synthesized with the counter-ion, BPh 4 À . In this case, the unsubstituted Cp 2 ZrMe þ system and the ethylenebridged bisindenyl system Et(Ind) 2 ZrMe þ are not active in polymerization.…”

Section: Structures Of Investigated Initiatorsmentioning

confidence: 99%

Polymerization of Methyl Methacrylate with Chloro Zirconocene Enolates

Ferenz¹,

Bandermann²,

Sustmann³

et al. 2004

Macro Chemistry & Physics

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Summary: The polymerization of methyl methacrylate (MMA) in the presence of the neutral chloro zirconocene enolates, Cp2ZrCl[OC(OMe)CMe2] (1), Me4C2(Cp)2ZrCl[OC(OMe)CMe2] (2), and Me2C(Cp)2ZrCl[OC(OMe)CMe2] (3), was investigated. None of these compounds is catalytically active on its own. They could be activated by adding Ph3CB(C6F5)4 (4); however, only if the initial concentration of enolate is higher than that of the perfluorated phenyl borate. Polymers were produced with a number average molar mass of up to 100 000 g/mol and a dispersion index of 1.1–1.3 with mixtures comprising 1 and 4 or 2 and 4. The degree of polymerization depends only on the quantity of excess enolate and not on the absolute concentration of the initiator components. In contrast, a mixture of 3 and 4 was not very active. Kinetic modeling of the systems as well as NMR spectroscopic investigations indicate that a bimetallic mechanism can describe chain growth. The activity of these catalytic systems depends on the structure of the ligand. The two zirconocenes with bridged cyclopentadienyl ligands, (2) and (3), convert MMA considerably slower. In addition to the methyl zirconocene enolates with unbridged cyclopentadienyl ligands, the corresponding chloro zirconocene enolates are also suitable for the polymerization of MMA. The latter compounds offer the advantage that preparations for the production of the initiators are comparatively simple.Structures of investigated initiators.magnified imageStructures of investigated initiators.

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A cationic bridged zirconocene complex as the catalyst for the stereospecific polymerization of methyl methacrylate

Cited by 31 publications

References 13 publications

Metal‐Catalyzed Group‐Transfer Polymerization: A Versatile Tool for Tailor‐Made Functional (Co)Polymers

Metal‐Catalyzed Group‐Transfer Polymerization: A Versatile Tool for Tailor‐Made Functional (Co)Polymers

Postulation of the Mechanism of the Selective Synthesis of Isotactic Poly(methyl methacrylate) Catalysed by [Zr{(Cp)(Ind)CMe2}(Me)(thf)](BPh4): A Hartree-Fock, MP2 and Density Functional Study

Polymerization of Methyl Methacrylate with Chloro Zirconocene Enolates

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