Ethylene copolymerizations with various pentenes [1-pentene, 4-methyl-1-pentene (4M1P), 3-methyl-1-pentene (3M1P), 4,4-dimethyl-1-pentene (NHEP)] using Cp*TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (1), CpTiCl 2 (Nd C t Bu 2 ) (2), [Me 2 Si(C 5 Me 4 )(N t Bu)]TiCl 2 (4) -MAO catalyst systems have been explored. Both 1 and 2 exhibited high catalytic activities affording high molecular weight copolymers with unimodal molecular weight distributions; the r E r C values (r E = k EE /k EC ; E = ethylene; C = comonomer) by 1 were small, suggesting that the monomer incorporations were rather alternating, whereas the copolymerization by 4 proceeded in a random manner (r E r C = ca. 1) except the copolymerization with 3M1P. 1 exhibited remarkable both catalytic activities and 3M1P incorporation in the ethylene/3M1P copolymerization, and the r E value (8.73) was much smaller than that by 4 (92), 2 (28.3). Both 1 and 4 showed better NHEP incorporations than 2 in the ethylene/NHEP copolymerization, and the rather large r E value by 2 (6.77) compared to those by 1 (2.58-2.94) was also obtained in the copolymerization with 4M1P. These results clearly indicate that the monomer reactivities (r E values) are influenced not only by the substituent in the olefins, but also by the nature of the catalytically active species (structure, and ligand set employed). Both 1 and 2 also exhibited notable catalytic activities in the copolymerization of ethylene with 1-dodecene, 1-hexadecene, affording high molecular weight copolymers with unimodal molecular weight distributions. No notable differences toward the r E values by 1,2,4 were seen, although the values were slightly affected by both the steric bulk of olefins (linear branching) and the catalyst structure employed.
Contents 1. Selected 1 H and 13 C NMR spectra for poly(ethylene-co-t-butylethylene)s prepared by using Cp′TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) [Cp′ = Cp* (1), t BuC 5 H 4 (2), 1,2,4-Me 3 C 5 H 2 (6)]-MAO catalyst systems. 2. Selected GPC profiles for poly(ethylene-co-t-butylethylene)s prepared by using Cp′TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) [Cp′ = Cp* (1), t BuC 5 H 4 (2), 1,2,4-Me 3 C 5 H 2 (6)]-MAO catalyst systems. 3. Selected DSC thermograms for poly(ethylene-co-t-butylethylene)s 4. 13 C NMR spectra for poly(1-hexene), poly(1-hexene-co-vinyltrimethylsilane), and poly(vinyltrimethylsilane) prepared by using ( t BuC 5 H 4 )TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (2) and CpTiCl 2 (N=C t Bu 2 ) (3)-MAO catalyst systems.
A series of phenoxy-substituted tris(pyrazolyl)borate titanium complexes, Tp′TiCl 2 (OAr) and Tp*TiMe 2 (OAr) [Tp ) HB(pyrazolyl) 3 , Tp* ) HB(3,5-Me 2 -pyrazolyl) 3 ; Ar ) Ph, 2,6-Me 2 C 6 H 3 , 2,6i Pr 2 C 6 H 3 ], were prepared, and their structures were determined by X-ray crystallography. These complexes exhibited from moderate to remarkable catalytic activities for ethylene polymerization in the presence of MAO; TpTiCl 2 (OPh) exhibited the highest catalytic activity for ethylene polymerization. The cationic Ti(IV)-methyl complex, [Tp*TiMe(O-2,6-Me 2 C 6 H 3 )] + [MeB(C 6 F 5 ) 3 ] -• (THF) 2 , polymerizes ethylene to give polyethylene with a uniform molecular weight distribution, clearly indicating that the cationic Ti(IV) species plays an essential role as the active species.
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