Early Metal Olefin Polymerization Catalysts

Long, R.J., Gibson, V.C., White, A.J.P., and Williams, D.J. (2006) Combining hard and soft donors in early-transition-metal olefin polymerization catalysts. Inorganic Chemistry, 45,511-513. 

Olefin-polymerization catalysts based on early transition metals) are a commercially important class of catalysts that are probably the most well-understood systems currently known. The metallocenes are the most common, but variations on the supporting ligand set are numerous. 

Perhaps the most important chemical property of these complexes is their potential as catalysts, particularly of the early transition metal isoleptic compounds for a-olefin polymerization. This arises because unlike the methyls, they are sufficiently stable to be used at temperatures where polymerization rates are adequate. Some data are summarized in Table VIII ( 9) TT-acceptor ligands are clearly disadvantageous. It will be seen that some of the systems are more active than Ziegler types, although stereoselectivity is poorer. 

In this contribution, we describe the discovery and application of phenoxy-imine ligated early transition metal complexes (FI catalysts) for olefin polymerization, including the concept behind our catalyst design, the discovery and the polymerization behavior of FI catalysts, and their applications to new polyolefinic materials. 

Fig. 1 Early examples of late transition metal olefin oligomerization and polymerization catalysts...

In order to incorporate polar-functionalized olefins, the catalyst system must exhibit tolerance to the functionality as described above. Therefore, polar monomer incorporation by the Ni(II) catalysts is generally not observed. Traces of methyl acrylate can be incorporated by the Ni(II) catalyst only under low loadings of that monomer [85], Acrylamide has been incorporated after prior treatment with tri-isobutylaluminum to block the amide donor sites, although polymerization activities are still relatively low [86], A similar protection of Lewis-basic functionalities by the coactivator has been cited to explain the copolymerization of certain monomers by early transition metal systems as well [40],... 

Olefin Polymerization by Early Transition Metal Catalysts... 

In contrast to the free-radical polymerizations, there have been relatively few studies on transition metal catalysed polymerization reactions in water. This is largely due to the fact that the early transition metal catalysts used commercially for the polymerization of olefins tend to be very water-sensitive. However, with the development of late transition metal catalysts for olefin polymerizations, water is beginning to be exploited as a medium for this type of polymerization reaction. For example, cationic Pd(II)-bisphosphine complexes have been found to be active catalysts for olefin-CO copolymerization [21]. Solubility of the catalyst in water is achieved by using a sulfonated phosphine ligand (Figure 10.5) as described in Chapter 5. 

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