Postmetallocene catalyst

More recently, postmetallocene catalyst systems, such as constrained-geometry complexes 4-6 (Fig. 7) [48-51], the polymeric (pentamethylcyclopentadi-... 

Postmetallocene catalysts can also facilitate this transformation [50, 60, 62], although they are typically less selective and a significant amount of acyclic hy-drosilylation product may form if the rate of silylation of the initial alkene insertion product A (Fig. 9) is competitive with the rate of carbocyclization. 

Fig. 20 Important postmetallocene catalysts for asymmetric aminoalkene hydroamination/...

Postmetallocene catalysts such as the bis(benzamidinato)yttrium alkyl 38 (Fig. 25) [201] have been studied with respect to their activity in these alkyne dimerizations as well (55). However, the catalytic activity is significantly lower in comparison to the lanthanocenes, and the catalyst is not applicable to nonhindered alkynes such as propyne. Larger substituents (e.g., Ph, Bu) as well as elevated temperatures are required [201]. 

Rare-Earth Metal Postmetallocene Catalysts with Chelating Amido Ligands... 

Based on the present development, we expect that the rapid development of new postmetallocene catalysts of the lanthanides will continue in the near future. 

As discussed earlier, ethylene propylene rubber (EPR or EPM) has been blended with PP and PE to improve the impact strength and to render the materials softer. Recently, metallocene catalysts or postmetallocene catalysts provide new pathways to generate elastic copolymers that can replace EPR. These pathways possess cheaper manufacturing cost and generate new materials with better compatibility to PP or PE. Such new materials included ethylene-propylene random copolymers with dominant ethylene component (33-34) or propylene-dominant component (35 1), propylene-ethylene block copolymer (42), ethylene-octene copolymer (43), poly(propylene-co-ethylene) (44), ethylene-hexene copolymer (45), ethylene-butene copolymer (46), low isotactic PP (47), and stereoblock PP (48). These materials are generally compatible with PP or PE, thus can be used to tailor the toughness (or the softness) of... 

Among the different postmetallocene catalysts in Figure 5.6, the complexes bearing phenoxyimine [17] ligands (FI catalysts) exhibit the highest ethylene polymerization activity. FI catalysts were developed by Fujita and coworkers [41] at Mitsui Chemicals, Japan, in the late 1990s. 

Continue the development toward commercialization of the new class of postmetallocene catalysts based on transition metal (Ti, Zr, Hf, V,. ..) complexes without Cp, but with imino-carboxylate and imino-amido ligands and sometimes with a neutral Lewis acid acting as a co-catalyst (Makio and Fujita 2009 Makio et al. 2011 Ivanchev et al. 2012). These systems are capable efficiently polymerized monomers containing polar group. Furthermore, different reactions are possible, e.g., anionic polymerization, ring-opening polymerization, or polycondensation. 

Brookhart et al. reported on Pd(II) and Ni (II) R-diimine catalysts (DuPont s Versipol catalyst) for copolymerization of C2, R-olefins, cycloolefin, and functionalized olefins. This postmetallocene catalyst does not need co-catalyst/activator, such as MAO... 

Li, T., Jenter, J., Roesky, P., 2010. Rare-earth metal postmetallocene catalysts with chelating amido ligands. In Roesky, P.W. (Ed.), Molecular Catalysis of Rare-Earth Elements. Springer, Berlin. 

Figure 16 Selected late transition metal postmetallocene catalysts of industrial interest.

Alkenes and/or alkynes can be dimerized, telomerized, and polymerized under palladium-catalysis. In an effort to copolymerize polar co-monomers, Johnson et al. investigated catalysts based upon palladium. These catalysts were referred to as postmetallocene catalysts. They were based upon complexes bearing bulky, neutral, alpha-diimine (or diketimine) ligands. They have been commercialized as DuPont s Versipol olefin polymerization system. The commercial synthesis of 1-octene (starting in 2007) is a palladium-catalyzed telomerization of butadiene with methanol. ... 

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