Polymerization activators for

The highest ethylene polymerization activity for a tetradentate salen-type group 4 complex was reported for silica supported (64) (600gmmol-1h bar ).193 Activities for a range of related zirconium and titanium complexes such as (65)-(67) are typically an order of magnitude lower.194-196... 

Weiss et al. [6] tested kaolinite and montmoriUonite as support materials, TIBA andTMAas cocatalysts, and different metallocenes (Cp2ZrCl2, Cp2ZrHCl, Cp2TiCl2) as catalysts. They found out that montmoriUonite produces supported catalysts with considerably higher polymerization activities than kaolinite. TIBA-treated MMT, in particular, had higher polymerization activity for propylene compared to TMA-treated MMT. 

Another main source of difference in clay performance is their surface acidities. Jeong et al. [50] compared two clays with different acidities from two different suppliers. They found out that clay acidity played a significant role in polymerization activity for the acidic clay sample, irrespective of its water content, polymerization activity was always observed, while no activity was found when the catalyst was supported on the basic clay sample. 

Table 1. Ethylene Polymerization Activities for Aluminoxane-Activated Unsubstituted Metallocenes 115...

The propylene oxide polymerization activity for each complex is shown in Scheme 24.10. Surprisingly, isostructural complexes 7 and Shad significantly different polymerization activities 7 achieved... 

Although the molecular clamp CD does not exhibit polymerization activity for 6-VL, it assists polymerization by anchoring the polymer chain and securing the active site. On the other hand, when 50 equivalents of adamantane (Ad) molecules as competitive guests were mixed with the ot,p-TPA-dimer and 50 equivalents of 6-VL in a reaction tube in the solid state, the a,p-TPA-dimer with Ad did not show polymerization activity for 6-VL (Figure 12.15c) due to the inhibition of monomer recognition by including Ad in the pCD cavity. 

We have been well immersed in the world of polymerization by Ni(0) and Pd(0) a-diimine complexes, starting with Keim s work in 1981, and continuing with the famous DuPont blockbuster WO 9623010 A2 (1 Aug 1996), but what about some of the less heralded catalyst systems One patent which surely must rate alongside the DuPont patent, and which provides a lucid demonstration of the fragility of the metalloeene concept as an answer to all polymerization catalyst problems, is Occidental s WO 9633202 (24 Oct 1996). Here the inventors explicitly state that they have encountered high polymerization activity for ethylene and -olefin monomers in complexes not heretofore expected to show any catalytic activity whatsoever, namely a range of simple. 

The polymerization activities for several ansa-titanocene complexes have been reported by Miyashita, Mabika, and Suzuki [22]. The catalytic activity increases by decreasing the bite angle, the angle of the Cp centroid-Tl-Cp centroid (Table 2.5). The activities of ansa-titanocene complexes are lower than those of the monocyclopentadienyl complexes. 

Table 5 Ethylene oligo- and polymerization activities for catalysts depicted in Scheme 36...

Liu B, Sindelar P, Fang Y, Hasebe K, Terano M Correlation of oxidation states of surface chromium species with ethylene polymerization activity for Phillips CrO /SiOa catalysts modified by Al-alkyl cocat yst, J Mol Catal A Chem 238(1-2) 142-150, 2005. 

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