Synthesis and structural analysis of phenoxy-substituted half-titanocenes with different anionic ligands, Cp*TiX(Y)(O-2,6-iPr2C6H3): Effect of anionic ligands (X,Y) in ethylene/styrene copolymerization

Nomura, Kotohiro; Pracha, Supathana; Phomphrai, Khamphee; Katao, Shohei; Kim, Dong-Hyun; Kim, Hyun Joon; Suzuki, Naohiro

doi:10.1016/j.molcata.2012.08.022

Cited by 16 publications

(7 citation statements)

References 96 publications

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“…These results indicated that the cationic Ti(IV) catalyst is again both kinetically and thermodynamically favorable for the styrene insertion into the polyethylene-coordinated intermediate. This is consistent with the previous studies that the styrene–ethylene copolymerization is catalyzed by Ti(IV) species and is consistent with our previous experiment that the formation of Ti(III) species was dependent on the concentration of the styrene monomer. , …”

Section: Resultssupporting

confidence: 94%

Theoretical Studies of Reaction Mechanisms for Half-Titanocene-Catalyzed Styrene Polymerization, Ethylene Polymerization, and Styrene–Ethylene Copolymerization: Roles of the Neutral Ti(III) and the Cationic Ti(IV) Species

Nakatani

Tomotsu

et al. 2021

Organometallics

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Reaction mechanisms of styrene polymerization, ethylene polymerization, and styrene–ethylene copolymerization catalyzed by the half-titanocene [(Me5C5)TiCl2(OAr)] complex were studied based on density functional theory (DFT) calculations. Neutral Ti(III), cationic Ti(IV), and ion-paired Ti(IV) [Ti(IV)-B(C6F5)4] complexes were examined as candidates of the active species in styrene and ethylene insertion reactions to investigate the influence of oxidation states in catalytic activity and selectivity. Our results clearly indicated that the cationic Ti(IV) species gives the highest catalytic activity for ethylene polymerization, which is consistent with previous studies. This is because of the higher Lewis acidity of the Ti(IV) center and the presence of a C–H agostic interaction to stabilize the transition state for the insertion reaction. On the other hand, only the neutral Ti(III) species is able to explain the high stereoselectivity in syndiospecific styrene polymerization (SSP), though both the Ti(III) and the Ti(IV) species are catalytically active for styrene polymerization. With the results from our previous XANES study, it is concluded that the neutral Ti(III) species produced by reduction of the Ti(IV) catalyst in the presence of styrene is the most plausible active species for SSP. In the Ti(IV) species, the activation energies of styrene and ethylene insertion reactions to polyethylene and ethylene insertion reaction to polystyrene were estimated to be very close to each other, suggesting that the Ti(IV) species is a plausible active species either for ethylene polymerization or styrene–ethylene copolymerization.

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Section: Resultssupporting

confidence: 94%

Theoretical Studies of Reaction Mechanisms for Half-Titanocene-Catalyzed Styrene Polymerization, Ethylene Polymerization, and Styrene–Ethylene Copolymerization: Roles of the Neutral Ti(III) and the Cationic Ti(IV) Species

Nakatani

Tomotsu

et al. 2021

Organometallics

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“…The similar effect was also observed in the syndiospecific styrene polymerization using ( t BuC 5 H 4 )TiCl 2 (O-2,6- i Pr 2 C 6 H 3 )–[PhN(H)Me 2 ]-[B(C 6 F 5 ) 4 ] catalyst [43]. Use of a mixture of Al( n -C 8 H 17 ) 3 /Al i Bu 3 cocatalyst was also effective for exclusive obtainment of copolymers with high styrene contents in the ethylene/styrene copolymerization even at high temperature [44,45]. It was assumed that the Al alkyl would also play a role to stabilize the catalytically active species for the subsequent decomposition by reacting with borate [46,47,48].…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Ultrahigh Molecular Weight Polymers with Low PDIs by Polymerizations of 1-Decene, 1-Dodecene, and 1-Tetradecene by Cp*TiMe2(O-2,6-iPr2C6H3)–Borate Catalyst

2019

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Polymerizations of 1-decene (DC), 1-dodecene (DD), and 1-tetradecene (TD) by Cp*TiMe2(O-2,6-iPr2C6H3) (1)–[Ph3C][B(C6F5)4] (borate) catalyst have been explored in the presence of Al cocatalyst. The polymerizations of DC and DD, in n-hexane containing a mixture of AliBu3 and Al(n-C8H17)3, proceeded with high catalytic activities in a quasi-living manner, affording high molecular weight polymers (activity 4120–5860 kg-poly(DC)/mol-Ti·h, Mn for poly(DC) = 7.04–7.82 × 105, after 20 min at −30 °C). The PDI (Mw/Mn) values in the resultant polymers decreased upon increasing the ratio of Al(n-C8H17)3/AliBu3 with decreasing the activities at −30 °C. The PDI values also became low when these polymerizations were conducted at low temperatures (−40 or −50 °C); high molecular weight poly(DD) with low PDI (Mn = 5.26 × 105, Mw/Mn = 1.16) was obtained at −50 °C. The TD polymerization using 1–borate–AliBu3 catalyst (conducted in n-hexane at −30 °C) afforded ultrahigh molecular weight poly(TD) (Mn = 1.02 × 106, Mw/Mn = 1.38), and the PDI values also decreased with increasing the Al(n-C8H17)3/AliBu3 ratio.

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“…On the basis of our previous reports on the synthesis of ethylene/styrene copolymers with high styrene contents, two phenoxide-modified half-titanocenes, ( t BuC 5 H 4 )TiCl 2 (OAr) ( 1 , Ar = 2,6- i Pr 2 C 6 H 3 ) and (1,2,4-Me 3 C 5 H 2 )TiCl 2 (OAr) ( 2 ), have been chosen for ethylene copolymerization with 2-vinylnaphthalene (VN). The Cp* analogue, Cp*TiCl 2 (OAr) ( 3 ), , which displays unique characteristics in ethylene copolymerization with substituted α-olefins, , and the linked half-titanocene called constrained geometry type (CGC), [Me 2 Si(C 5 Me 4 )(N t Bu)]TiCl 2 ( 4 , also expressed as A in Scheme ), known as a typical catalyst for ethylene copolymerization with styrene , as well as α-olefins, has also been chosen for comparison. These polymerizations were conducted in toluene in the presence of AlMe 3 -free MAO white solid (d-MAO), ,, and the results are summarized in Table . , As observed in styrene polymerization − as well as in ethylene/styrene copolymerization, − ,,− the polymerization by MAO itself gave the atactic homopolymer (run 1), poly(VN), and the resulting polymers prepared by the catalytic reactions were thus washed with 2-butanone (methyl ethyl ketone, MEK) using a centrifuge.…”

Section: Resultsmentioning

confidence: 99%

“…Ethylene/styrene copolymers are considered interesting materials because the viscoelastic behavior and thermomechanical properties can be modified by incorporation of styrene into the polyethylene backbone . Linked half-titanocenes (called “constrained geometry type”, complexes A – C , Scheme ), ,− ,− certain ansa -metallocenes (exemplified as complexes D and E ), , and modified half-titanocenes (exemplified as 1 , 2 , F – H ) − are known to be effective group 4 transition-metal catalysts for copolymerization . In particular, bimetallic-linked half-titanocene ( C ) − ,, and phenoxide-modified half-titanocenes ( 1 , 2 ), shown in Scheme , have been known to be effective catalysts in terms of synthesis of copolymers with high styrene contents (>50 mol %) .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Amorphous Ethylene Copolymers with 2-Vinylnaphthalene, 4-Vinylbiphenyl and 1-(4-Vinylphenyl)naphthalene

Aoki

Nomura

2020

Macromolecules

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Ethylene copolymerization with 2-vinylnaphthalene (VN) by ( t BuC 5 H 4 )TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (1)−MAO catalyst system afforded high-molecular-weight amorphous copolymers with unimodal molecular weight distributions as well as uniform compositions (M n = 18 100−39 900, M w /M n = 1.23−1.47, T g = 24−75 °C, VN 21.6−44.8 mol %). Copolymerization with 4vinylbiphenyl (VB) using 1− and (1,2,4-Me 3 C 5 H 2 )TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (2)−MAO catalyst systems also yielded highmolecular-weight copolymers (M n = 96 200−222 000, M w /M n = 1.33−2.06), and synthesis of the copolymers with high VB contents (>50 mol %) has been demonstrated. These copolymerizations in the presence of a [Me 2 Si(C 5 Me 4 )(N t Bu)]TiCl 2 (4)−MAO catalyst system afforded semicrystalline polymers (possessing melting temperatures of 91−103 °C). Linear relationships between the glass transition temperature (T g ) and the comonomer (VN, VB) content have been demonstrated. The T g values in the same comonomer content increased in the order VN > VB > styrene, suggesting that introduction of an aromatic substituent to the side pendent group affects the thermal properties (T g values). These copolymers possess resonances ascribed to repeated VN (VB) incorporations on the basis of microstructural analysis of poly(ethylene-co-VN)s and poly(ethylene-co-VB)s through 13 C nuclear magnetic resonance (NMR) spectra, and the regioselectivity as well as the degree of the head-to-tail repeated insertions is affected by the cyclopentadienyl fragment and the comonomer (VN, VB, styrene) employed. Synthesis of high-molecular-weight amorphous poly(ethylene-co-VB) with high VB content, which possesses high T g with a uniform composition (M n = 130 000, M w /M n = 1.51, T g = 156 °C, VB 87.5 mol %), has thus been attained by copolymerization using the 2−MAO catalyst system.

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Synthesis and structural analysis of phenoxy-substituted half-titanocenes with different anionic ligands, Cp*TiX(Y)(O-2,6-iPr2C6H3): Effect of anionic ligands (X,Y) in ethylene/styrene copolymerization

Cited by 16 publications

References 96 publications

Theoretical Studies of Reaction Mechanisms for Half-Titanocene-Catalyzed Styrene Polymerization, Ethylene Polymerization, and Styrene–Ethylene Copolymerization: Roles of the Neutral Ti(III) and the Cationic Ti(IV) Species

Theoretical Studies of Reaction Mechanisms for Half-Titanocene-Catalyzed Styrene Polymerization, Ethylene Polymerization, and Styrene–Ethylene Copolymerization: Roles of the Neutral Ti(III) and the Cationic Ti(IV) Species

Synthesis of Ultrahigh Molecular Weight Polymers with Low PDIs by Polymerizations of 1-Decene, 1-Dodecene, and 1-Tetradecene by Cp*TiMe2(O-2,6-iPr2C6H3)–Borate Catalyst

Synthesis of Amorphous Ethylene Copolymers with 2-Vinylnaphthalene, 4-Vinylbiphenyl and 1-(4-Vinylphenyl)naphthalene

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