Synthesis of Butene−Ethylene and Hexene−Butene−Ethylene Copolymers from Ethylene via Tandem Action of Well-Defined Homogeneous Catalysts

Komon, Zachary J. A.; Bu, Xianhui; Bazan, Guillermo C.

doi:10.1021/ja994222c

Cited by 164 publications

(92 citation statements)

References 22 publications

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“…Homogeneous ''tandem catalysis'' has also received attention as an alternative approach to branched polyethylenes. Here, a single-site catalytic center produces ␣-olefin oligomers, which are subsequently incorporated, via an intermolecular process, into highmolecular-weight polyethylene by a second, different single-site catalytic center present in the same reaction medium and using the same ethylene feed (26)(27)(28). It should be evident that, at typical polymerization concentrations, these intermolecular tandem processes are inherently inefficient.…”

Section: Binuclear Structures and Macromolecular Branch Formation In mentioning

confidence: 99%

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Marks

2006

Proc. Natl. Acad. Sci. U.S.A.

225

109

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A series of bimetallic organo-group 4 ''constrained geometry'' catalysts and binuclear bisborane and bisborate cocatalysts have been synthesized to probe catalyst center-catalyst center cooperativity effects on olefin enchainment in homogenous olefin polymerization and copolymerization processes. Significant nuclearity effects are found versus mononuclear controls, and the effect can be correlated with metal-metal approach distances and ion pairing effects. Novel polymer structures can be obtained by using such binuclear catalyst͞cocatalyst systems.catalysis ͉ polymer ͉ polyolefin E nzymes achieve superior reactivity and selectivity, in part, by their efficacy in creating high local reagent concentrations and special, conformationally advantageous active site-substrate proximities and interactions (1-4). In this regard, the possibility of unique and more efficient abiotic catalytic transformations based on cooperative effects between adjacent active centers in multinuclear transition metal complexes is currently of great interest. Within the context of the rapidly advancing and technologically significant field of homogeneous single-site olefin polymerization catalysis (5-10), the conjecture that cooperative effects involving two or more metal centers in close proximity might achieve more efficient chain propagation and͞or novel polymer architectures motivated the research that is the subject of this contribution. Single-Site Olefin Polymerization ProcessesOne of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense development of new polymerization technologies based on well defined single-site metallocene and coordination complex olefin polymerization catalysts (5-10). The active catalytic species is typically generated by combining a transition-metal organometallic precursor with an activator or cocatalyst. The resulting electrophilic͞coordinatively unsaturated, strongly ionpaired species then undergoes rapid olefin enchainment. In optimum cases (e.g., group 4 metal and cyclopentadienyl-type ligand), catalysts with truly exceptional productivities and selectivities for high-molecular-weight polyolefins are produced. Constrained Geometry Catalysts: Testbeds for Multinuclear Cooperativity EffectsGroup 4 ''constrained geometry'' catalysts (CGCs) (A; Fig. 1) are well known single-site polymerization agents (16, 17) that produce unusual branched, hence far more processable, polyethylenes with high productivity and selectivity. One of the key features of these catalysts is the coordinatively open nature of the active site, which allows rapid enchainment of sterically encumbered olefin comonomers into the polyethylene backbone. Under certain conditions, these catalysts yield vinyl-terminated, chain-transferred macromonomers (a macromolecule that acts as a monomer) that diffuse away and then undergo competitive reinsertion into a growing polymer chain to produce macromolecules with long chain branching (Fig. 19, which is published ...

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Section: Binuclear Structures and Macromolecular Branch Formation In mentioning

confidence: 99%

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Marks

2006

Proc. Natl. Acad. Sci. U.S.A.

225

109

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“…Bazan and coworkers 83,84 developed a tandem catalyst approach for the synthesis of polyolefins with con- Figure 6. Influence of P E on the polymer topology in the polymerization of ethylene with the Pd-bisimine chain-walking catalyst.…”

Section: Branched Polymers By the Tandem Action Of Multiple Catalystsmentioning

confidence: 99%

Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

Guan

2003

J. Polym. Sci. A Polym. Chem.

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ABSTRACT:In this article, recent examples are reviewed of late-transition-metal catalysis applied to polymer topology control. By the judicious selection or design of latetransition-metal catalysts, polymers with a broad range of topologies, including linear, short-chain-branched, hyperbranched, dendritic, and cyclic topologies, have been successfully synthesized. A distinctive advantage of the catalyst approach is that polymers with complex topologies can be prepared in one pot from simple commercial monomers. A fundamental difference of the catalyst approach with respect to other approaches is that the polymer topology is controlled by the catalysts instead of the monomer structure. In our own laboratory, we have successfully used two strategies to control the polymer topology with late-transition-metal catalysts. In the first strategy, hyperbranched polymers are prepared by the direct free-radical polymerization of divinyl monomers through control of the competition between propagation and chain transfer with a cobalt chain-transfer catalyst. In the second strategy, polyethylene topology is successfully controlled by the regulation of the competition between propagation and chain walking with the Brookhart Pd II -␣-bisimine catalyst.

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“…The complementary oligomerization component to 9 was discovered when it was observed that the ethylene consumption rate of [(C 6 H 5 ) 2 PC 6 H 4 C(OB (C 6 F 5 ) 3 )O-j 2 P,O]Ni(g 3 -CH 2 CMeCH 2 ) (10) was within the same order of magnitude as that of 9. [40] Compound 10 is readily obtained by the reaction of [(C 6 H 5 ) 2 PC 6 H 4 C(O)Oj 2 P,O]Ni(g 3 -CH 2 CMeCH 2 ) (11) [41] with B(C 6 F 5 ) 3 . f Mol-% branching is the moles of a-olefin inserted into the polymer backbone divided by the total number of olefins (ethylene and a-olefins) that comprise the backbone, multiplied by 100.…”

Section: Tandem Catalysis Of Lldpe With Welldefined Single Site Catalmentioning

confidence: 99%

Synthesis of Branched Polyethylene by Tandem Catalysis

Komon

Bazan

2001

Macromol. Rapid Commun.

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105

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Synthesis of Butene−Ethylene and Hexene−Butene−Ethylene Copolymers from Ethylene via Tandem Action of Well-Defined Homogeneous Catalysts

Cited by 164 publications

References 22 publications

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

Synthesis of Branched Polyethylene by Tandem Catalysis

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