Propene polymerization, zirconocene

Table 11 Propene polymerizations catalyzed by the phosphine-borane zirconocene 161e...

Fig. 17. Origin of stereospecificity in propene polymerization by ethylenebisfindenyl) zirconocen-dichloride the growing polymer chain forces the inserting monomer into an orientation resulting in the relative topicity like for insertion...

Voegele, J. Dietrich, U. Hackmann, M. Rieger, B. Design of Ethylene-bridged ansa-Zirconocene Dichlorides for a Controlled Propene Polymerization Reaction. In Metallocene-based Polyolefins Preparation, Properties and Technology, Scheirs, J., Kaminsky, W., Eds. Wiley Chichester, 2000 Vol. 1, p485. 

Gureea, G. Longo, P. Cavallo, L. Corradini, P. Resconi, L. Relationship between regiospecificity and type of stereospecificity in propene polymerization with zirconocene-based catalysts. J. Am. Chem. Soc. 1997, 119, 4394. 

Rieger, B. Jany, G. Fawzi, R. Steimann, M. Unsymmetric ani a-zirconocene complexes with chiral ethylene bridges influence of bridge conformation and monomer concentration on the stereoselectivity of the propene polymerization reaction. Organometallics 1994, 13, 647. 

Table 6. Propene Polymerization with rac-Bisindenyl Zirconocene/MAO Catalysts Influence of Indene...

Table 7. Propene Polymerization with Representative Bis(2-arylindenyl)zirconocene/MAO Catalysts...

Elastomeric Polypropene. To model the propene polymerization to elastomeric polypropene catalyzed by bis(2-arylindenyl)zirconocenes ° or Ci-symmetric Me2X(Cp)(l-Ind) metallocenes, the consecutive two-state model originally described by Coleman and... 

Propene Polymerization with Metallocene Table 17. Propene Polymerization with Zirconocene/MAO Catalysts Synthesis and Microstructure ... 

Hence, eq 4 corresponds to a reaction order higher than 1 on monomer concentration for Ap,fast[M] > Af—s > Ap,siow[M] > As—f, that is, when the slower state of the catalytic center is of lower energy with respect to the faster one, and the interconversion rate between the fast and the slow state is intermediate between the fast and the slow chain propagation rates. Figure 48 shows three series of experimental activity data for propene polymerization, obtained with zirconocenes of three different symmetries, and their best fit to eq 4. 

Leclerc, M. K. Brintzinger, H. H. an a-Metallocene derivatives. 31. Origins of stereoselectivity and stereoerror formation in anra-zirconocene-catalyzed isotactic propene polymerization. A deuterinm labeling study. J. Am. Chem. Soc. 1995, 777, 1651-1652. 

Toto, M. Cavallo, L. Corradini, P. Moscardi, G Resconi, L. Guerra, G Influence of n-Hgand substitutions on the regiospecificity and stereospecificity in isospecific zirconocenes for propene polymerization. A molecular mechanics analysis. Macromolecules 1998,31,3431-3438. 

Alt, H. G. Zenk, R. C2-symmetric bis(fluorenyl) complexes Four complex models as potential catalysts for the isospecific polymerization of propylene. J. Organomet. Chem. 1996, 512, 51-60. Chen, Y.-X. Rausch, M. D. Chien, J. C. W. C2y- and C2-Symmetric an5a-bis(fluorenyl)zirconocene catalysts Synthesis and a-olefin polymerization catalysis. Macromolecules 1995, 28, 5399-5404. Rieger, B. Stereospecific propene polymerization with rac-[l,2-bis(ti -(9-fluorenyl))-l-phenylethane] zirconium dichloride/methylalumoxane. Polym. Bull. (Berlin) 1994,32,41 6. 

Rieger, B. Repo, T. Jany, G. Ethylene-bridged ansa-zirconocene dichlorides for syndiospecific propene polymerization. Polym. Bull. 1995, 35, 87-94. 

Kaminsky, W. Rabe, O. Schauwienold, A.-M. Schupfner, G U. Hanss, J. Kopf, J. Crystal structure and propene polymerization characteristics of bridged zirconocene catalysts. J. Organomet. Chem. 1995,497,181-193. 

For some leading reviews see (a) Resconi, L. Cavallo, L. Fait, A. Piemontesi, F. Selectivity in propene polymerization with metallocene catalysts. Chem. Rev. 2000,100, 1253-1345. (b) Alt, H. G Koppl, A. Effect of the nature of metallocene complexes of Group IV metals on their performance in catalytic ethylene and propylene polymerization. Chem. Rev. 2000, 100, 1205-1221. (c) Halterman, R. L. Synthesis and applications of chiral cyclopentadienyhnetal complexes. Chem. Rev. 1992, 92, 965-994. (d) Halterman, R. L. Synthesis of chiral titanocene and zirconocene dichlorides. In Metallocenes ... 

Lieber, S. Brintzinger, H. H. Propene polymerization with catalyst mixtures containing different ansa-zirconocenes Chain transfer to aUcylaluminum cocatalysts and formation of stereoblock polymers. Macromolecules 2000, 33, 9192-9199. 

Carvill, A. Tritto, I. Locatelli, R Sacchi, M. C. Polymer microstructure as a probe into hydrogen activation effect in aw a-zirconocene/methylaluminoxane catalyzed propene polymerizations. Macrvmolecules 1997, 30, 7056-7062. 

The development of Ziegler-Natta-type catalysts (see Section 25.8) has, since the 1980s, included the use of zirconocene derivatives. In the presence of methylaluminoxane [MeAl(p-0)] as a co-catalyst, compounds A, B and C (shown below) are active catalysts for propene polymerization. Compounds A and B are chiral because of the relative orientations of the two halves of the organic ligand. A racemic mixture of A facilitates the formation of isotactic pol3fpropene, while use of catalyst C results in syndiotactic polypropene (see Section 25.8 for definitions of syndiotactic, isotactic and atactic). If... 

In the zirconocene-catalyzed polymerization of alkenes, Landis and coworkers [20] have reported in situ observation of a Zr-polymeryl species, 15, at 233 K (Figure 1.5). Complex 15 is formed by partial reaction of 14 with excess 1-hexene. Derivatives 16 and 17 are generated quantitatively from 15 by addition of ca. 10 equiv. of propene and ethene, respectively. No other intermediates, such as alkene complexes, secondary alkyls, diasteromers of 15 or 16, or termination products, accumulate to detectable levels. These NMR studies permit direct monitoring of the initiation, propagation and termination processes, and provide a definitive distinction between intermittent and continuous propagation behavior. 

Removable Amount of Zirconocene by Washing of Me2C(CpFlu)ZrCl2/MAO-SiC>2 Measured by Polymerization Activity of Propene... 

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