Scandium-Catalyzed Regio- and Stereospecific <i>cis</i>-1,4-Polymerization of 1,3-Cyclohexadiene and Copolymerization with Ethylene

Li, Xiaofang; Hou, Zhaomin

doi:10.1021/ma101835e

Cited by 32 publications

(18 citation statements)

References 40 publications

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“…The copolymerization of ethylene with isoprene by 1e-Sc/[Ph 3 C][B(C 6 F 5 ) 4 ] yielded for the first time alternating isoprene−ethylene copolymers (Scheme 3e), 8b and the copolymerization of CHD with ethylene afforded the first random CHD−ethylene copolymers with high cis-1,4 selectivity (Scheme 3f). 24 Copolymerizations of ethylene with cyclic olefins such as norbornene and dicyclopentadiene took place in an alternating fashion with extremely high activity (Scheme 3g,h). 25,26 The sequential copolymerization of styrene and ε-caprolactone in the presence of 1e-Sc or 1f-Sc with [Ph 3 C][B(C 6 F 5 ) 4 ] afforded diblock copolymers with well-controlled molecular weight and molecular weight distribution (Scheme 4).…”

Section: Articlementioning

confidence: 99%

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

2015

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The search for new catalysts for more efficient, selective chemical transformations and for the synthesis of new functional materials has been a long-standing research subject in both academia and industry. To develop new generations of catalysts that are superior or complementary to the existing ones, exploring the potential of untapped elements is an important strategy. Rare-earth elements, including scandium, yttrium, and the lanthanides (La-Lu), constitute one important frontier in the periodic table. Rare-earth elements possess unique chemical and physical properties that are different from those of main-group and late-transition metals. The development of rare-earth-based catalysts by taking the advantage of these unique properties is of great interest and importance. The most stable oxidation state of rare-earth metals is 3+, which is difficult to change under many reaction conditions. The oxidative addition and reductive elimination processes often observed in catalytic cycles involving late transition metals are generally difficult in the case of rare-earth complexes. The 18-electron rule that is applicable to late-transition-metal complexes does not fit rare-earth complexes, whose structures are mainly governed by the sterics (rather than the electron numbers) of the ligands. In the lanthanide series (La-Lu), the ionic radius gradually decreases with increasing atomic number because of the influence of the 4f electrons, which show poor shielding of nuclear charge. Rare-earth metal ions generally show strong Lewis acidity and oxophilicity. Rare-earth metal alkyl and hydride species are highly reactive, showing both nucleophilicity and basicity. The combination of these features, such as the strong nucleophilicity and moderate basicity of the alkyl and hydride species and the high stability, strong Lewis acidity, and unsaturated C-C bond affinity of the 3+ metal ions, can make rare-earth metals unique candidates for the formation of excellent single-site catalysts. This Account is intended to give an overview of our recent studies on organo rare-earth catalysis, in particular the synthesis and application of half-sandwich rare-earth alkyl complexes bearing monocyclopentadienyl ligands for olefin polymerization, carbometalation, and hydroarylation. Treatment of half-sandwich rare-earth dialkyl complexes having the general formula CpMR2 with an equimolar amount of an appropriate borate compound such as [Ph3C][B(C6F5)4] can generate the corresponding cationic monoalkyl species, which serve as excellent single-site catalysts for the polymerization and copolymerization of a wide range of olefin monomers such as ethylene, 1-hexene, styrene, conjugated and nonconjugated dienes, and cyclic olefins. The cationic half-sandwich rare-earth alkyl complexes can also catalyze the regio- and stereoselective alkylative alumination of alkenes and alkynes through insertion of the unsaturated C-C bond into the metal-alkyl bond followed by transmetalation between the resulting new alkyl or alkenyl species and an alkylaluminum...

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Section: Articlementioning

confidence: 99%

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

2015

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“…33–36 Consequently, most of the resulting CHD‐based copolymers are constructed with both 1,2‐CHD and 1,4‐CHD composing units. In general, the coordination‐insertion copolymerization of CHD is an effective method to yield high performance CHD‐based copolymer with controllable regio‐/stereoselectivity and microstructure . To the best of our knowledge, coordination‐insertion copolymerization of CHD with styrene has been much less extensively investigated.…”

Section: Resultsmentioning

confidence: 99%

“…In 2010, Li and Hou reported the regio-and stereoselective polymerization of CHD catalyzed by cationic half-sandwich cyclopentadienyl scandium alkyl catalysts. 26 Later, our group investigated the catalytic reactivity of half-sandwich fluorenyl rare earth metal dialkyl complexes Flu 0 Ln(CH 2 SiMe 3 ) 2 (THF) n (1a-1j) in combination with 1 equiv. of activator such as [Ph 3 C][B(C 6 F 5 ) 4 ], [PhNHMe 2 ][B(C 6 F 5 ) 4 ], or B(C 6 F 5 ) 3 and Ali-Bu 3 [Fig.…”

Section: Polymerization Of Chdmentioning

confidence: 99%

Novel cationic rare earth metal alkyl catalysts for precise olefin polymerization

Yang

2017

J. Polym. Sci. Part A: Polym. Chem.

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This mini‐review provides recent progress in the synthesis of rare earth metal dialkyl complexes and their application as highly efficient and regio‐/stereoselective catalysts in the coordination‐insertion (co)polymerization of olefins such as styrene, isoprene, 1,3‐cyclohexadiene, and ocimene. Through modifying the coordination atom, the ligand skeleton, and the substitutent on the skeleton of the chelating ligand, tuning the electron density and the steric environment around the rare earth metal center, the precise control of the activity and regio‐/stereoselectivity of the (co)polymerization as well as the comonomer incorporation and sequence distribution of the resulting copolymers are achieved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2271–2280

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“…Anionic, free-radical, and transition metal catalyzed polymerizations are common methods for polymerizing 1,3-CHD. [90][91][92][93][94][95] Anionic polymerization methods result in microstructures with 1,2 and 1,4-linkages whereas certain metal-based catalysts can produce predominately 1,4-linkages. The presence of 1,4-sequences in the polymer can serve as a precursor to polyparaphenylene.…”

Section: Cyclohexadienementioning

confidence: 99%

How well can renewable resources mimic commodity monomers and polymers?

Mathers

2011

J. Polym. Sci. A Polym. Chem.

223

100

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This highlight discusses the recent progress aimed at maximizing the potential of biomass for commodity monomers and polymers. These efforts are no longer solely academic issues. In recent years, a variety of alkene, diene, aromatic, and condensation type monomers have utilized renewable resources, such as cellulose, lignin, plant oils, starches, and monoterpenes in commercial polymers. Generally, these multifaceted efforts involve pretreatment of biomass with thermal, chemical, or physical methods followed by a catalyst sequence that entails a combination of acid-catalysis, bio-catalysis, or metal-based catalysis. In this regard, synthesis strategies for ethylene, propylene, a-olefins, methylmethacrylate, 1,3-butadiene, 1,3-cyclohexadiene, isoprene, 1,3-propanediol, 1,4-butanediol, and terephthalic acid are discussed as well as opportunities for other renewable-based monomers. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] 2012

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Scandium-Catalyzed Regio- and Stereospecific cis-1,4-Polymerization of 1,3-Cyclohexadiene and Copolymerization with Ethylene

Cited by 32 publications

References 40 publications

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Half-Sandwich Rare-Earth-Catalyzed Olefin Polymerization, Carbometalation, and Hydroarylation

Novel cationic rare earth metal alkyl catalysts for precise olefin polymerization

How well can renewable resources mimic commodity monomers and polymers?

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