Zur kinetik der polyreaktion von styrol mit löslichen ziegler‐natta‐katalysatoren. I.

Reichert, Von K. H.; Berthold, J.; Dornow, V.

doi:10.1002/macp.1969.021210120

Cited by 12 publications

(1 citation statement)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…'~ A number of studies of the kinetically simpler type, those catalysts derived from ethyl or higher dkyl compounds, have been published. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Even if consideration is confined to this class of catalysts, the existing literature appears to be contradictory on several points. Although there is general agreement that the active site involves an alkylated Ti(1V) moiety and that the Ti(II1) species formed by its reduction is catalytically inactive,s evidence that valence reduction is the primary cause of loss of activity is more circumstantial than d i r e~t .~-~ Oxygen at ppm levels has been reported to affect these catalysts,14-16 but many workers have not reported its concentration in their s t~d i e s .~-l~ The effect of excess aluminum alkyl has not been settled.…”

Section: Introductionmentioning

confidence: 99%

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts

Waters

Mortimer

1972

J. Polym. Sci. A‐1 Polym. Chem.

View full text Add to dashboard Cite

SynopsisSoluble ethylene polymerization catalysts derived from (r-C&)*Ti(R)Cl and It'AlCL where R is ethyl or higher alkyl and R' may be methyl or ethyl, were studied both by polymerization kinetics at 0°C and by diagnostic experiments. An early acceleration in rate occmred a t this temperature in toluene solvent which wm due to a solvent dependent increase in catalyst activity] not to a gradual formation of catalyst. No such solvent effect was found in nonaromatic solvents. The subsequent decay in rate, at least at low temperatures] did not depend upon valence reduction. The efFect of Al/Ti ratio was studied, and certain discrepancies in the literature were shown to be due to the method of making kinetic measurements. Oxygen, which has previously been reported to affect the polymerization rate with these catalysts, was also found to eliminate the acceleration period in toluene when present in the amount of 1% of the catalyst. These catalysts gave polymers a t low temperature for which the active site had long l i e and which did not undergo chain transfer. Therefore, they approximate many of the characteristics of living polymers.

show abstract

Section: Introductionmentioning

confidence: 99%

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts

Waters

Mortimer

1972

J. Polym. Sci. A‐1 Polym. Chem.

View full text Add to dashboard Cite

show abstract

Stereospezifische Olefinpolymerisation mit chiralen Metallocenkatalysatoren

et al. 1995

View full text Add to dashboard Cite

Untersuchungen an neuen Metallocenkatalysatoren zur Polymerisation von α‐Olefinen haben gegenwärtig weitreichende Auswirkungen auf die Entwicklung neuer Materialien und auch auf unser Verständnis der grundlegenden Reaktionsmechanismen, die für das Wachstum von Polymerketten an einem Katalysatorzentrum und für deren Stereoregularität verantwortlich sind. Im Gegensatz zu heterogenen Ziegler‐Natta‐Katalysatoren erfolgt die Polymerisation mit einem homogenen Metallocenkatalysator im Prinzip an einheitlichen Metallzentren mit definierter Koordinationssphäre. Dies macht es möglich, die Struktur der Metallocenkomplexe mit den Eigenschaften des Polymers, beispielsweise Molekulargewicht, stereochemischer Mikrostruktur, Kristallisationsverhalten und mechanischen Eigenschaften, zu korrelieren. Mit homogenen Katalysatorsystemen können Regio‐ und Stereoregularitäten, Molekulargewichte, Molekulargewichte, Molekulargewichtsverteilungen und Einbauverhältnisse von Comonomeren wirksam kontrolliert werden. Diese Katalysatoren eröffnen neue Zugänge zur Homo‐ und Copolymerisation cyclischer Olefine, zur Cyclopolymerisation von Dienen und sogar zu funktionalisierten Polyolefinen und erweitern somit das Spektrum und die Vielseitigkeit technisch verfügbarer Polyolefin‐Materialien.

show abstract

Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts

Brintzinger

Fischer²,

Mülhaupt

et al. 1995

Angew. Chem. Int. Ed. Engl.

2,748

1,645

View full text Add to dashboard Cite

The cover picture shows an autostereogram representation of the X-ray crystal structure of the smallest [2]catenane yet isolated. The catenane is formed in one step in an eight-molecule condensation from commercially available reagents and is isolated by simple washing and filtration of the reaction mixture. More about this catenane and analogously accessible [2]catenanes with differing dynamic properties is reported by D. A. Leigh et al. in two consecutive communications on p. 1209 ff. To see the 3-D image you must stare through the picture so that your focal point is behind the page. Placing the picture behind a piece of glass and focusing on your reflection helps if you cannot see the picture straight away. The autostereogram image is 2 x 108 times larger than the molecule itself. Did you see the molecule depicted here? REVIEWS Con tentsStereo-and regioregularity, molecular weight and molecular weight distribution of polyolefins, and incorporation of comonomers can be controlled efficiently with ansa-metallocene catalysts. Catalysts of this type can also be used for the polymerization of cyclic olefins and the production of functionalized polyolefins. In contrast to classical heterogeneous Ziegler-Natta catalysis, metallocene-catalyzed olefin polymerization occurs on uniform metal centers having a defined coordination environment. Recent research in this area has provided insights into fundamental mechanisms as well as advances in practical applications of this class of catalysts. ContentsTwo catena-like interpenetrating enantiomorphic frameworks of condensed tetragonal antiprisms. RhBi,,,, form the basis of the crystal structure of RhBi,. The electron localization function (ELF) shows high localization of the valence electrons only on the periphery of the frameworks (lone pairs of Bi atoms), whereas the electrons inside the nets are delocalized. The periodic nodal surface (PNS) I,-Y** describes perfectly the hyperbolic organization of the entire RhBi, structure. It separates the regions with low electron localization inside the polyhedral nets from the hyperbolic layer of the lone pairs.The optical rotation of poly(propy1ene imine) dendrimers with 64 identical enantiomerically pure amino acid end groups tends to zero. This remarkable behavior results from the packing of the end groups in the highly dense, multiply hydrogenbonded surface, which gives rise to different frozen-in conformations, leading to an internal compensation of optical activity.The condensation of eight molecules in one step provides 1, the smallest [2]catenane to date, in 20 YO yield. The cavity in one of the identical macrocycles of the catenane has dimensions of 4 x 6 A. Electrophilic a-alkylation and nucleophilic 1,2-addition to glycol aldehyde 1 (P = protecting group) affords syn-l,2-amino alcohols 2 in good yields and with high selectivities (89 to > 99% de, 94 to 2 9 9 % ee). This method, in which 1 is first converted into a chiral hydrazone, provides a flexible, direct route to y-amino-P-hydroxycarboxylic acids such as statin 3, an...

show abstract

Zur kinetik der polyreaktion von styrol mit löslichen ziegler‐natta‐katalysatoren. I.

Cited by 12 publications

References 14 publications

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts

Stereospezifische Olefinpolymerisation mit chiralen Metallocenkatalysatoren

Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts

Contact Info

Product

Resources

About

Zur kinetik der polyreaktion von styrol mit löslichen ziegler‐natta‐katalysatoren. I.

Cited by 12 publications

References 14 publications

Study of (π‐C5H5)2Ti(C2H5)Cl and its higher homologs in soluble Ziegler catalysts

Study of (π‐C5H5)2Ti(C2H5)Cl and its higher homologs in soluble Ziegler catalysts

Stereospezifische Olefinpolymerisation mit chiralen Metallocenkatalysatoren

Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts

Contact Info

Product

Resources

About

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts

Study of (π‐C₅H₅)₂Ti(C₂H₅)Cl and its higher homologs in soluble Ziegler catalysts