Propene polymerization, zirconocene catalyzed

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. 

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

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... 

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. 

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. 

Ziegler-Natta catalysts have long remained the only organometallic catalysts in macromolecular chemistry. The area was revolutionized by the discovery that zirconocene derivatives catalyze the polymerization of propene. At the same time, strong industrial interest has prompted a worldwide development in the field. The first polymers based on metallocene-type catalysts have recently appeared on the market under the names Hostacen (Hoechst AG), Exact (Exxon), and Affinity (Dow). The metals zirconium and hafnium appear to be the most important metals in synthetic preparations. 

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