Copolymerization of Ethylene with α-Olefins Containing Various Substituents Catalyzed by Half-Titanocenes: Factors Affecting the Monomer Reactivities

Abstract

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.

Half-Titanocenes Containing Anionic Ancillary Donor Ligands: Effective Catalyst Precursors for Ethylene/Styrene Copolymerization

“…[80], but also exhibited efficient comonomer incorporations for copolymerization of ethylene with α-olefin [81][82][83], as well as with styrene [52][53][54][55][56] in the presence of MAO (Scheme 1). [52,53], whereas the Cp* analogue (4), which exhibited remarkable activities and comonomer incorporations in ethylene/α-olefin copolymerization [80][81][82][83], exhibited lower activities than 1-3 (Table 1) [52][53][54][55][56]. The resultant polymers are poly(ethylene-co-styrene)s exclusively without by-producing polyethylene and/or syndiotactic polystyrene [52,53].…”

Oxovanadium(IV) complexes with [ONNO]-chelating ligands as catalysts for ethylene homo- and copolymerization

“…2 that the molecular weight of polyethylene obtained with [VO(acacen)]/EtAlCl 2 is much higher than that for copolymers, and that it decreases with the increase of comonomer concentration in the feed. Such effects were observed repeatedly for copolymerizations catalyzed by different catalytic systems [21,[35][36][37][38]. Lower molecular weights of polymers for increasing 1-octene concentrations may result from the chain transfer to comonomer and/or more favourable β-hydride elimination after comonomer incorporation.…”

Microstructure of Copolymers of Norbornene Based on Assignments of 13C NMR Spectra: Evolution of a Methodology

“…[41][42][43][44][45] In particular, 4-methylcyclohexene (4-MeCHE) and 1-methylcyclopentene (1-MeCPE) copolymers have been synthesized recently with nonbridged half-titanocenes containing anionic donor ligands of type, Cp'TiX2(Y) (Cp' = cyclopentadienyl group, Y = aryloxo, ketimide, phosphinimide etc.) [46].…”