Late-metal catalysts for ethylene homo- and copolymerization.

B. Anionic Ligands 302 IX. Group 9 Catalysts 302 X. Group 10 Catalysts 303 A. Neutral Ligands 303 1. R-Diimine and Related Ligands 303 2. Other Neutral Nitrogen-Based Ligands 304 3. Chelating Phosphorus-Based Ligands 304 B. Monoanionic Ligands 305 1. [PO] Chelates 305 2. [NO] Chelates 306 3. Other Monoanionic Ligands 306 4. Carbon-Based Ligands 306 XI. Group 11 Catalysts 307 XII. Group 12 Catalysts 307 XIII. Group 13 Catalysts 307 XIV. Summary and Outlook 308 XV. Glossary 308 XVI. References 308

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Advances in non-metallocene olefin polymerization catalysis.

One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

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Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMXn (M = Fe, X = Cl, n = 2, 3, X = Br, n = 2; M = Co, X = Cl, n = 2), bearing chelating 2,6-bis(imino)pyridyl ligands L [L = 2,6-(ArNCR1)2C5H3N] is reported. X-ray diffraction studies show the geometry at the metal centers to be either distorted square pyramidal or distorted trigonal bipyramidal. Treatment of the complexes LMXn with methylaluminoxane (MAO) leads to highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE). LFeX2 precatalysts with ketimine ligands (R1 = Me) are approximately an order of magnitude more active than precatalysts with aldimine ligands (R1 = H). Catalyst productivities in the range 3750−20600 g/mmol·h·bar are observed for Fe-based ketimine catalysts, while Co ketimine systems display activities of 450−1740 g/mmol·h·bar. Molecular weights (Mw) of the polymers produced are in the range 14000−611000. Changing reaction ...

Iron and cobalt ethylene polymerization catalysts bearing 2,6-bis(imino)pyridyl ligands : synthesis, structures, and polymerization studies

Carbon dioxide is a clean and versatile solvent for the synthesis and processing of a range of materials. This review focuses on recent advances in polymer synthesis and processing using liquid and supercritical CO2. The synthetic techniques discussed include homogeneous solution polymerisation, precipitation polymerisation, dispersion and emulsion polymerisation, and bulk polycondensation. The formation of porous polymers and polymer blends is also considered, and the specific advantages of CO2 in these processes are evaluated in each case. The use of CO2 as a solvent for polymer processing is reviewed from a materials perspective, with particular attention being given to the formation of polymers with well defined morphologies. The variable solvent strength associated with supercritical fluids has been utilised in areas such as polymer fractionation and polymer extraction. Plasticisation phenomena have been exploited for the impregnation and heterogeneous chemical modification of polymeric materials. The formation of microcellular polymer foams by pressure induced phase separation is considered, as is the use of CO2 for polymer particle formation, spray coating, and microlithography. The aim of the review is to highlight the wide range of opportunities available to the materials chemist through the use of carbon dioxide as an alternative solvent.

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Polymer synthesis and processing using supercritical carbon dioxide

Mechanistic aspects of palladium-catalyzed insertion copolymerizations of ethylene and α-olefins with methyl acrylate to give high molar mass polymers are described. Complexes [(N∧N)Pd(CH2)3C(O)OMe]BAr‘4 (2) or [(N∧N)Pd(CH3)(L)]BAr‘4 (1:  L = OEt2; 3:  L ⋮ NCMe; 4:  L ⋮ NCAr‘) (N∧N ≡ ArNC(R)−C(R)NAr, e.g., Ar ⋮ 2,6-C6H3(i-Pr)2, R ⋮ H (a), Me (b); Ar‘ ⋮ 3,5-C6H3(CF3)2) with bulky substituted α-diimine ligands were used as catalyst precursors. The copolymers are highly branched, the acrylate comonomer being incorporated predominantly at the ends of branches as −CH2CH2C(O)OMe groups. The effects of reaction conditions and catalyst structure on the copolymerization reaction are rationalized. Low-temperature NMR studies show that migratory insertion in the η2-methyl acrylate (MA) complex [(N∧N)PdMe{H2CCHC(O)OMe}]+ (5) occurs to give initially the 2,1-insertion product [(N∧N)PdCH(CH2CH3)C(O)OMe]+ (6), which rearranges stepwise to yield 2 as the final product upon warming to −20 °C. Activation parameters (ΔH⧧ = ...

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Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and α-Olefins with Methyl Acrylate

Copolymerization of Ethylene and Acrylates by Nickel Catalysts

Certain complexes containing ligands having a phosphino group, amino group or an imino group, and a second functional group such as amide, ester or ketone, when complexed to transition metals, catalyze the (co)polymerization of olefinic compounds such as ethylene, α-olefins and/or acrylates. A newly recognized class of ligands for making copolymer containing polar monomers using late transition metal complexes is described.

Polymerization of olefinic compounds

Ethylene and allyl- or vinylsilanes are efficiently copolymerized by certain late transition metal complexes containing selected bidentate or tridentate ligands. The resulting novel polymers may be crosslinked by moisture when vinylsilane contains groups bound to silicon which are hydrolyzable. The polymers are useful for wire coating, crosslinked foams, pipes, and other uses.

Copolymers of olefins and vinyl- and allylsilanes

Ethylene and norbornene-type monomers are efficiently copolymerized by certain metal complexes, particularly nickel complexes, containing selected anionic and neutral bidentate ligands. The polymerization process is tolerant of polar functionality on the norbornene-type monomer and can be carried out at elevated temperatures.

Lin Wang

Papers

Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and α-Olefins with Methyl Acrylate

Copolymerization of Ethylene and Acrylates by Nickel Catalysts

Polymerization of olefinic compounds

Copolymers of olefins and vinyl- and allylsilanes

Copolymers of ethylene with various norbornene derivatives