Kaminsky-type polymerizations catalysts

Fluorinated ligands have often been employed in olefin polymerization. Fluorine substituents on the aromatic ring in well-refined Kaminsky-type metallocence catalysts for olefin polymerization play an important role in controlling the activity of the catalysts, molecular weight, tacticity, and molecular weight distribution of the polymers [28]. The catalyst (67),... 

The utility of the Tebbe type complex in carbonyl olefination is discussed in Chapter 4. The bridged complex may be regarded as a special type of a carbene complex where the Cp2Ti=CH2 unit is masked by interaction with the AlMe2Cl entity. Formation of the Tebbe s complex suggests the occurrence of a-hydrogen elimination in the preparation of the Ziegler-Natta and Kaminsky type olefin polymerization catalysts from titanium chlorides and methylaluminum compounds. 

Lohrenz, J. C. W. Woo, T. K. Ziegler, T. A density functional study of the origin of the propagation barrier in the homogeneous ethylene polymerization with Kaminsky-type catalysts. J. Am. Chem. Soc. ms, 117, 12793-12780. 

To better understand the polymerization process and to be able to rationally design better catalyst systems, single-site homogeneous catalyst systems were developed as models of the heterogeneous systems employed commercially. Of particular interest were metallocene-type catalysts, which had been discovered to be slightly active for polymerizations in the early work of Natta et Until the accidental discovery of MAO by Sinn, Kaminsky and coworkers in 1980, however, the activity of metallocene catalysts was far too low to be useful. Activation of a metallocene precursor such as (ri -C5H5)2ZrCl2 with MAO was found to yield extremely active polymerization catalysts, and the number of metallocene-type catalysts reported in the literamre has since exploded. ... 

Metallocene Catalysts. Higher a-olefins can be polymerized with catalyst systems containing metallocene complexes. The first catalysts of this type (Kaminsky catalysts) include metallocene complexes of zirconium such as biscyclopentadienylzirconium dichloride, activated by methylaluminoxane. These catalysts polymerize a-olefins with the formation of amorphous atactic polymers. Polymers with high molecular weights are produced at decreased temperatures and have rubber-like properties. 

Scheme 1.28. Polymerization of propylene with Kaminsky-Brintzinger type catalyst.

Cyclic olefins undergo a very unusual type of ring-opening polymerization in the presence of certain transition metal catalysts (Olfstead, 1988 Kaminsky et al., 2012 Novak et al., 1992 Ivin, 1983 Bhowmick et al., 2001). This is illustrated in Eq. (2.90) for the ring-opening metathesis polymerization (ROMP)... 

Catalysts that yield highly syndiotactic polypropylene (86% racemic pentads) were also developed. One of them is /-propylene(ri -cyclopentadienyl-r fluorenyl)zirconium dichloride [291]. Initial disclosures of metallocene catalysts were followed by numerous publications in the literature that described similar materials for the polymerizations of either ethylene or propylene, or both, and for formation of various copolymers. Thus, for instance, Kaminsky et al. [292], reported preparaticm of a zirconium dichloride-type catalyst for copolymerization of cyclic olefins with ethylene. These cyclic olefins are cyclopentene, norbomene, and the hindered cyclopentadiene adducts of norbomene [292]. The catalytic system consists of a bridged indene derivative that is combined with methylaluminoxane ... 

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