The Effect of SiMe₃ and SiEt₃Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide‐Modified Half‐Titanocenes

Abstract

Remarkable effects of SiMe 3 and SiEt 3 parasubstituents in the phenoxide-modified half-titanocenes, Cp*TiCl 2 (O-2,6-i Pr 2-4-R-C 6 H 2) [R= SiMe 3 (6), SiEt 3 (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 8C showed higher than those conducted at 25 8C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 8C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81 10 5 kg-polymer mol À1-Ti h, M n = 6.55-10.0 10 4 , DC-OH 2.3-3.6 mol %). Scheme 1. Synthesis of Cp*TiCl 2 (O-2,6-i Pr 2-4-R-C 6 H 2). R = Ph (3), CHPh 2 (4), CPh 3 (5), SiMe 3 (6), SiEt 3 (7)].

Effect of para‐Substituents in Ethylene Copolymerizations with 1‐Decene, 1‐Dodecene, and with 2‐Methyl‐1‐Pentene Using Phenoxide Modified Half‐Titanocenes‐MAO Catalyst Systems

“…In particular, the SiMe 3 analogue ( 6 ) showed a notable increase in the activity at 50 °C (8.04×10 5 →1.44×10 6 kg‐polymer/mol‐Ti⋅h). As reported previously, [19] the notable activities were observed by the SiMe 3 ( 6 ) and SiEt 3 ( 7 ) analogues at 50 °C even under the low catalyst concentration conditions (runs 17 vs 18, 21 vs 22). The resultant polymers were poly(E‐ co ‐DC)s that possess relatively high molecular weights with unimodal molecular weight distributions ( M n =1.38‐1.97×10 5 ; M w / M n =1.48‐1.85) as well as with high DC contents (20.1–21.4 mol %).…”

“…A series of the half‐titanocene dichloride complexes containing different para ‐substituents on the 2,6‐diisopropylphenoxy ligand, Cp*TiCl 2 (O‐2,6‐ i Pr 2 ‐4‐R‐C 6 H 2 ) [R=H ( 1 ), t Bu ( 2 ), Ph ( 3 ), CHPh 2 ( 4 ), CPh 3 ( 5 ), SiMe 3 ( 6 ), SiEt 3 ( 7 ), 4‐ t BuC 6 H 4 ( 8 ), 3,5‐Me 2 C 6 H 3 ( 9 )], have been chosen for this study. Complexes 8 and 9 were newly prepared according to the analogous procedure for syntheses of 1–7 , [7,19,20] by treating Cp*TiCl 3 with the corresponding lithium phenoxides in Et 2 O; the ligands, HO‐2,6‐ i Pr 2 ‐4‐(4‐ t BuC 6 H 4 )−C 6 H 2 and HO‐2,6‐ i Pr 2 ‐4‐(3,5‐Me 2 C 6 H 3 )−C 6 H 2 were prepared from HO‐2,6‐ i Pr 2 −4−Br−C 6 H 2 by coupling reactions in the presence of Pd catalysts (Scheme 2) (details are shown in the Experimental Section). The prepared complexes were identified by NMR spectra and elemental analysis.…”

“…Figure 2 shows selected 13 C NMR spectra (in 1,1,2,2‐tetrachloroethane‐ d 2 at 110 °C) of poly(ethylene‐ co ‐DC)s prepared by 1 (at 25 °C), [19] 9 (at 50 °C), and Figure 3 shows the spectra of poly(ethylene‐ co ‐DD)s by 1 , 2 – MAO catalyst systems (at 25 °C). Additional 13 C NMR spectra of poly(ethylene‐ co ‐DC)s and poly(ethylene‐ co ‐DD)s by 4 – 7 , 9 at 25 and 50 °C are also shown in Figures S2‐1‐S2‐11 in the Supporting Information [24] .…”

“…50 °C for removing toluene, Me 3 Al, and then heated at >100 °C for 1 h for completion) in the drybox to give d‐MAO white solids [7b,9b] . Cp*TiCl 2 (O‐2,6‐ i Pr 2 C 6 H 3 ) ( 1 ), [7b] Cp*TiCl 2 (O‐2,6‐ i Pr 2 ‐4‐ t BuC 6 H 2 ) ( 2 ), [20] Cp*TiCl 2 (O‐2,6‐ i Pr 2 ‐4‐R‐C 6 H 2 ) [R=Ph ( 3 ), CHPh 2 ( 4 ), CPh 3 ( 5 ), SiMe 3 ( 6 ), SiEt 3 ( 7 )] [19] and 4‐Br‐2,6‐ i Pr 2 C 6 H 2 OH [19] were prepared according to the reported procedure.…”

Analysis of Ethylene Copolymers with Long-Chain α-Olefins (1-Dodecene, 1-Tetradecene, 1-Hexadecene): A Transition between Main Chain Crystallization and Side Chain Crystallization

“…The activities conducted at 50 °C were higher than those conducted at 25 °C, as observed in copolymerization with DD and 9-decen-1-ol. 30 The ethylene copolymers (with DD, TD, and HD) with various contents were thus prepared by adopting this catalyst system. Homopolymerizations with TD and HD also afforded poly(TD) and poly(HD) (runs 29 and 40, respectively).…”