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3667 KiB

Open AccessFeature PaperArticle

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine

by Kuo-Hsuan Yu, Shou-Ling Huang, Yi-Hung Liu, Yu Wang, Shiuh-Tzung Liu, Yuan-Chung Cheng, Ya-Fan Lin and Jwu-Ting Chen

Molecules 2017, 22(7), 1095; https://doi.org/10.3390/molecules22071095 - 30 Jun 2017

Cited by 10 | Viewed by 5458

Abstract

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino–pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH₂(o-C₆H₄N)]Pd(C₇ [...] Read more.

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino–pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH₂(o-C₆H₄N)]Pd(C₇H₁₀Me)(NCMe)}(BF₄) (R = ⁱPr (2a), ^tBu (2b), Ph (2c), 2,6-Me₂C₆H₃ (2d), 2,6-ⁱPr₂C₆H₃ (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a–1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination–recoordination of amino–pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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1071 KiB

Open AccessArticle

Synthesis and Characterization of Constrained Geometry Oxygen and Sulphur Functionalized Cyclopentadienylchromium Complexes and Their Use in Catalysis for Olefin Polymerization

by Ruiguo Zhao, Jun Ma, Hao Zhang and Jiling Huang

Molecules 2017, 22(5), 856; https://doi.org/10.3390/molecules22050856 - 22 May 2017

Cited by 7 | Viewed by 4850

Abstract

A series of constrained geometry O-functionalized cyclopentadienylchromium complexes (1–6) and a S-functionalized cyclopentadienylchromium complex (7) were first synthesized, characterized, and tested as catalyst precursors for the olefin polymerization. In the presence of MAO, the complexes exhibited high [...] Read more.

A series of constrained geometry O-functionalized cyclopentadienylchromium complexes (1–6) and a S-functionalized cyclopentadienylchromium complex (7) were first synthesized, characterized, and tested as catalyst precursors for the olefin polymerization. In the presence of MAO, the complexes exhibited high catalytic activity for the polymerization of ethylene. It is shown that ligand variations can have a substantial effect on catalyst activity and stability. The effect of Al/Cr ratio on catalytic activity was also studied. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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3317 KiB

Open AccessArticle

Isotactic and Syndiotactic Alternating Ethylene/Propylene Copolymers Obtained Through Non-Catalytic Hydrogenation of Highly Stereoregular cis-1,4 Poly(1,3-diene)s

by Giovanni Ricci, Antonella Caterina Boccia, Giuseppe Leone, Ivana Pierro, Giorgia Zanchin, Miriam Scoti, Finizia Auriemma and Claudio De Rosa

Molecules 2017, 22(5), 755; https://doi.org/10.3390/molecules22050755 - 06 May 2017

Cited by 10 | Viewed by 5440

Abstract

The homogeneous non-catalytic hydrogenation of cis-1,4 poly(isoprene), isotactic cis-1,4 poly(1,3-pentadiene) and syndiotactic cis-1,4 poly(1,3-pentadiene) with diimide, formed by thermal decomposition of para-toluenesulfonylhydrazide, is examined. Perfectly alternating ethylene/propylene copolymers having different tacticity (i.e., isotactic and syndiotactic), which are difficult to [...] Read more.

The homogeneous non-catalytic hydrogenation of cis-1,4 poly(isoprene), isotactic cis-1,4 poly(1,3-pentadiene) and syndiotactic cis-1,4 poly(1,3-pentadiene) with diimide, formed by thermal decomposition of para-toluenesulfonylhydrazide, is examined. Perfectly alternating ethylene/propylene copolymers having different tacticity (i.e., isotactic and syndiotactic), which are difficult to synthesize by stereospecific copolymerization of the corresponding monomers, are obtained. Both isotactic and syndiotactic alternating ethylene/propylene copolymers are amorphous, with very low glass transition temperatures. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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9194 KiB

Open AccessArticle

Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization

by Kuo-Tseng Li and Ling-Huey Wu

Molecules 2017, 22(5), 751; https://doi.org/10.3390/molecules22050751 - 05 May 2017

Cited by 5 | Viewed by 4255

Abstract

Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong [...] Read more.

Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong mass transfer limitations. This study aims to improve the activity of supported CGC catalysts by using nanometer-sized silica. Ti[(C₅Me₄)SiMe₂(N^tBu)]Cl₂, a “constrained-geometry” titanium catalyst, was supported on MAO-treated silicas (nano-sized and micro-sized) by an impregnation method. Ethylene homo-polymerization and co-polymerization with 1-octene were carried out in a temperature range of 80–120 °C using toluene as the solvent. Catalysts prepared and polymers produced were characterized. For both catalysts and for both reactions, the maximum activities occurred at 100 °C, which is significantly higher than that (60 °C) reported before for supported bis-cyclopentadienyl metallocene catalysts containing zirconium, and is lower than that (≥140 °C) used for unsupported Ti[(C₅Me₄)SiMe₂(N^tBu)]Me₂ catalyst. Activities of nano-sized catalyst were 2.6 and 1.6 times those of micro-sized catalyst for homopolymerization and copolymerization, respectively. The former produced polymers with higher crystallinity and melting point than the latter. In addition, copolymer produced with nanosized catalyst contained more 1-octene than that produced with microsized catalyst. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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1029 KiB

Open AccessArticle

Quasi-Living Polymerization of Propene with an Isotactic-Specific Zirconocene Catalyst

by Kei Nishii, Miyuki Murase and Takeshi Shiono

Molecules 2017, 22(5), 725; https://doi.org/10.3390/molecules22050725 - 02 May 2017

Cited by 1 | Viewed by 4299

Abstract

Propene polymerization with isotactic (iso)-specific C₂-symmetric rac-Me₂Si(2-Me-Benz(e)-Ind)₂ZrCl₂ (1) and rac-Me₂Si(2-Me-4-Ph-1-Ind)₂ZrCl₂ (2) were conducted under various conditions for achieving iso-specific living polymerization of [...] Read more.

Propene polymerization with isotactic (iso)-specific C₂-symmetric rac-Me₂Si(2-Me-Benz(e)-Ind)₂ZrCl₂ (1) and rac-Me₂Si(2-Me-4-Ph-1-Ind)₂ZrCl₂ (2) were conducted under various conditions for achieving iso-specific living polymerization of propene. When Complex 1 was activated with trialkylaluminum-free modified methylaluminoxane (dMMAO) at −40 °C, the number-average molecular weight (M_n) linearly increased against the polymerization time to reach M_n = 704,000 within 15 min of polymerization, although the molecular weight distributions was broad (M_w/M_n < 3). Thus, it was found that quasi-living polymerization of propene proceeded in the 1-dMMAO system. The living nature of iso-polypropene was confirmed by the block copolymerization, where the M_n value increased from 221,000 to 382,000 after the addition of 1-octene to yield the block copolymer with a melting point of 150 °C. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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574 KiB

Open AccessArticle

N-(2,2-Dimethyl-1-(quinolin-2-yl)propylidene) arylaminonickel Complexes and Their Ethylene Oligomerization

by Hongyi Suo, Tong Zhao, Yiqing Wang, Qing Ban and Wen-Hua Sun

Molecules 2017, 22(4), 630; https://doi.org/10.3390/molecules22040630 - 13 Apr 2017

Cited by 11 | Viewed by 4118

Abstract

A series of N-(2,2-dimethyl-1-(quinolin-2-yl)propylidene) arylamines was sophisticatedly synthesized and reacted with nickel(II) bromine for the formation of the corresponding nickel complexes. All the organic compounds were characterized by IR, NMR spectra and elemental analysis, while all the nickel complexes were characterized by [...] Read more.

A series of N-(2,2-dimethyl-1-(quinolin-2-yl)propylidene) arylamines was sophisticatedly synthesized and reacted with nickel(II) bromine for the formation of the corresponding nickel complexes. All the organic compounds were characterized by IR, NMR spectra and elemental analysis, while all the nickel complexes were characterized by IR spectra and elemental analysis. On activation with ethylaluminium sesquichloride (EASC) and modified methylaluminoxane (MMAO), all nickel precatalysts exhibited good activities toward ethylene oligomerization, indicating the positive efficiency of gem-dimethyl substitutents; in which major hexenes were obtained with MMAO. The catalytic parameters were verified, and the steric and electronic influences of substituents with ligands were observed, with a slight change of activities under different ethylene pressures. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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1914 KiB

Open AccessArticle

Preparation of “Constrained Geometry” Titanium Complexes of [1,2]Azasilinane Framework for Ethylene/1-Octene Copolymerization

by Seul Lee, Seung Soo Park, Jin Gu Kim, Chung Sol Kim and Bun Yeoul Lee

Molecules 2017, 22(2), 258; https://doi.org/10.3390/molecules22020258 - 09 Feb 2017

Cited by 19 | Viewed by 5633

Abstract

The Me₂Si-bridged ansa-Cp/amido half-metallocene, [Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂, termed a “constrained-geometry catalyst (CGC)”, is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent [...] Read more.

The Me₂Si-bridged ansa-Cp/amido half-metallocene, [Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂, termed a “constrained-geometry catalyst (CGC)”, is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent is joined by the Si-bridge, were prepared, and the catalytic performances of these species was studied. Me₄C₅HSi(Me)(CH₂CH=CH₂)-NH(C(R)(R’)CH=CH₂) (R, R’ = H or methyl; Me₄C₅H = tetramethylcyclopentadienyl) was susceptible to ring closure metathesis (RCM) when treated with Schrock’s Mo-catalyst to afford -Si(Me₄C₅H)(Me)CH₂CH=CHC(R)(R’)NH- containing a six-membered ring framework. Using the precursors and the products of RCM, various CGC derivatives, i.e., [-Si(η⁵-Me₄C₅)(Me)CH₂CH=CHC(R)(H)N-]TiMe₂ (13, R = H; 15, R = Me), [-Si(η⁵-Me₄C₅)(Me)CH₂CH₂CH₂CH₂N]TiMe₂ (14), [(η⁵-Me₄C₅)Si(Me)(CH₂CH=CH₂)NCH₂CH=CH₂]TiMe₂ (16), [(η⁵-Me₄C₅)Si (Me)(CH=CH₂)NCH₂CH=CH₂]TiMe₂ (17), and [(η⁵-Me₄C₅)Si(Me)(CH₂CH₃)NCH₂CH₂CH₃]TiMe₂ (18), were prepared. The catalytic activity of the newly prepared complexes was lower than that of CGC when activated with [Ph₃C][B(C₆F₅)₄]/iBu₃Al. However, the catalytic activity of these species was improved by using tetrabutylaluminoxane ([iBu₂Al]₂O) instead of iBu₃Al and the activity of 14/[Ph₃C][B(C₆F₅)₄]/[iBu₂Al]₂O was comparable to that of CGC/[Ph₃C][B(C₆F₅)₄]/iBu₃Al (4.7 and 5.0 × 10⁶ g/mol-Ti, respectively). Advantageously, the newly prepared complexes produced higher molecular weight poly(ethylene-co-1-octene)s than CGC. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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Review

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1703 KiB

Open AccessReview

Engineering of Syndiotactic and Isotactic Polystyrene-Based Copolymers via Stereoselective Catalytic Polymerization

by Eva Laur, Evgueni Kirillov and Jean-François Carpentier

Molecules 2017, 22(4), 594; https://doi.org/10.3390/molecules22040594 - 07 Apr 2017

Cited by 16 | Viewed by 8032

Abstract

This contribution presents an updated overview of the different copolymers containing stereoregular polystyrene blocks. Special emphasis is placed on syndiospecific and isospecific copolymerization of styrene with co-monomers (ethylene and α-olefins, conjugated and non-conjugated dienes, styrene derivatives, etc.). The catalytic systems involved are described [...] Read more.

This contribution presents an updated overview of the different copolymers containing stereoregular polystyrene blocks. Special emphasis is placed on syndiospecific and isospecific copolymerization of styrene with co-monomers (ethylene and α-olefins, conjugated and non-conjugated dienes, styrene derivatives, etc.). The catalytic systems involved are described and the polymerization mechanisms are discussed. Alternative approaches (simultaneous, living, chain-transfer and graft copolymerization) and the resulting detailed structures and characteristics of the copolymers are also reported. Full article

(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)

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