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Design, synthesis and evaluation of new Ziegler -Natta catalyst components
The compound (η5-pentamethylcyclopentadienyl)tin tetrakis(pentafluorophenyl)borate (2) has been synthesized. This cation proved to be an effective Ziegler/Natta α-olefin cocatalyst. Activities for ethylene polymerizations using dimethylzirconocene and 2 were 7.3 × 105 g PE/mol 2·[C2H4]·h at 20°C and 1.2 × 106 g PE/mol 2·[C2H 4]·h at 70°C. This system was also effective for the polymerization of propylene. Activities using rac-ethylenebis(indenyl)dimethylzirconium with the tin cation were 3.0 × 105 g PP/mol 2·[C 3H6]·h at 20°C. Activities increased markedly when using zirconocene dichlorides/tri(i-butyl)aluminum/ 2. Activities for ethylene polymerization using zirconocene dichloride/tri( i-butyl)aluminum/2 at 20°C were 7.0 × 10 6 g PE/mol 2·[C2H4]·h. Activities for the polymerization of propylene using rac-ethylenebis(indenyl)zirconium dichloride/tri(ibutyl)aluminum/2 at 20°C were 5.4 × 106 g PP/mol 2·[C3H6]·h. ^ Several titanium(IV) complexes of the type Cp′Ti(NMe 2)3 (Cp′-cyclopentadienyl (10 ), (dimethylaminoethyl)cyclopentadienyl (11), indenyl (12) and pentamethylcyclopentadienyl (13)) have been prepared and their catalytic properties in the polymerization of α-olefins examined. Complexes 10 and 11 catalyzed the polymerization of ethylene in the presence of MAO with much higher activity than 12 or 13. Complexes 12 and 13 polymerized ethylene with an activity similar to that of CpTiCl3. Also, 10 and 11 were used as ethylene/1-hexene copolymerization catalysts. Complex 10 effectively polymerized styrene with a higher activity and higher syndiospecificity than the other three catalysts. ^ Two new Ti(IV) complexes of the type (OCHRCH2N-2,6-Me 2Ph) Ti(NMe2)2 have been synthesized. The two complexes were studied as Ziegler-Natta type polymerization catalysts in the presence of an excess of methylaluminoxane. It was found that ethylene polymerization activity for both catalysts increased by increasing the polymerization temperature from 25 to 70°C. If the catalysts were pretreated with trimethylaluminum, the activities increased at 25°C, but decreased slightly at 70°C. Both complexes were found to be ineffective for the polymerization of propylene. An X-ray crystal structure of (OCH2CH2N-2,6-Me 2Ph)Ti(NMe2)2 shows the complex to be dimeric in the solid state. ^ Four titanium ansa-cyclopentadienyl-amido complexes of the general formula [C5H3RMe2SiN(2,6-Me 2C6H5)]TiX2 (R = H, Me, Bz, tBu; X = NMe2 or Cl) have been synthesized. The complexes polymerize both ethylene and propylene and were most active at lower temperatures. In general, the smaller the substituent on the cyclopentadienyl group, the more active the catalyst. The catalysts were found to be poorly stereoselective. ^
"Design, synthesis and evaluation of new Ziegler -Natta catalyst components"
(January 1, 2000).
Electronic Doctoral Dissertations for UMass Amherst.