Homopolymerization palladium catalysts

More recently, monometallic palladium catalysts " containing a sulfonated phosphine ligand have been developed that are able to homopolymerize ethylene and copolymerize ethylene with acrylates and other polar monomers in both solution and aqueous phase. In solution, the activity... 

Thus, until the last decade, three families of catalysts have been reported to catalyze the addition, or vinyl-type homopolymerization of norbornene resulting in poly(2,3-bicyclo[2.2.1]hept-2-ene). These three catalyst types are the classical TiC -based Ziegler systems (type 1), the zirconocene/aluminoxane systems (type 2) and certain electrophilic palladium(II) complexes (type 3). 

Brookhart and co-workers recently reported tantalizing results that were close to constituting true copolymerizations of ethylene and methyl acrylate. ° ° The catalyst employed was the palladium version of the diimine complexes that were previously reported for ethylene and a-olefin homopolymerizations (complexes IV). °° The close qualification... 

While a wide range of monomers have been incorporated in ethylene copolymerizations with the palladium a-diimine catalysts, there are also a variety of monomers which slow homopolymerization and are not incorporated into the polymer chain and others which inhibit all polymerization. There is a general trend that removing the polar functionality from the vicinity of the double bond lessens the rate penalty experienced in the copolymerizations. A superior approach is to place a group which blocks doublebond isomerization between the olefinic group and... 

Single site catalysts, such as metallocene compounds, CGCs, and nickel or palladium diimine complexes, used in combination with MAO or borate cocatalysts, are highly active for the homopolymerization of norbornene and its copolymerization with ethylene. The structure of the norbornene homo- and copolymers can be widely influenced by the symmetry and structure of the ligands on the transition metal complexes. 

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