Ziegler-Natta-type olefin polymerization catalysts

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. 

Brookhart and coworkers [1] have recently developed Ni(II) and Pd(II) bis-imine based catalysts of the type (ArN=C(R)-C(R)=NAr)M-CH3+ (la of Figure 1) that are promising alternatives to both Ziegler-Natta systems and metallocene catalysts for olefin polymerization. Traditionally, such late metal catalysts are found to produce dimers or extremely low molecular weight oligomers due to the favorability of the P-elimination chain termination process [2],... 

Uses. The main use for tetraorganotin compounds is as (usually captive) intermediates for the tri-, di-, and monoorganotins. Although there have been reports in the patent literature of the use of tetraorganotins as components of Ziegler-Natta-type catalysts for the polymerization of olefins, there is no evidence that such catalysts are used commercially. 

Catalysts of the Ziegler-Natta type are applied widely to the anionic polymerization of olefins and dienes. Polar monomers deactivate the system and cannot be copolymerized with olefins. J. L. Jezl and coworkers discovered that the living chains from an anionic polymerization can be converted to free radicals by the reaction with organic peroxides and thus permit the formation of block copolymers with polar vinyl monomers. In this novel technique of combined anionic-free radical polymerization, they are able to produce block copolymers of most olefins, such as alkylene, propylene, styrene, or butadiene with polar vinyl monomers, such as acrylonitrile or vinyl pyridine. 

Other Polyolefins. Virtually every available a-olefin has been polymerized with Ziegler/Natta-type catalysts. The polymers are of considerable scientific interest (17). but few have achieved commercial status. The following olefins are of particular interest. 

Of particular interest is the fact that many olefin metathesis catalyst systems are of the Ziegler—Natta type. This raises the question of the relationship between the mechanism of olefin metathesis and that of Ziegler-Natta polymerization this aspect is discussed in Ch. 4. 

The polymerization of olefins has long been one of the most industrially important applications of organometaiiic complexes.The use of transition metals as catalysts ranges from early metal (e.g., Ti, Zr) Ziegler-Natta type polymerizations to late-metal single site catalysts as well as atom transfer radical polymerizations (ATRPs)... 

Uses Catalyst component in Ziegler-Natta type systems for olefin and diene polymerizations in alkylation reactions as catalyst component in linear oligomerization and cyclization of unsat. hydrocarbons... 

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