Reactions of Olefins with the Titanium‐Carbon Bond

Bestian, H.; Clauß, Karl

doi:10.1002/anie.196307041

Cited by 28 publications

(2 citation statements)

References 12 publications

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“…Because of the higher tendency of late transition metal alkyls to undergo β-hydrogen abstraction, we examined early transition metal compounds as possible catalysts for the synthesis of hyperbranched polyethene. The titanium-based synthesis of branched polymers from ethene has been reported previously; however, the detailed structures of the polymers and the reaction mechanism were not investigated. , …”

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Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

et al. 2000

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Hyperbranched polyethene was synthesized using a novel TaCl 5 /alkylaluminum halide catalyst system. The polymers were viscous oils with a ratio of methyl hydrogens/total alkyl hydrogens of 0.25-0.40 and weight-average molecular weights of 600-4000 daltons. Both branching and molecular weight can be varied by changing reaction conditions and catalyst composition. The system can also be modified to synthesize 1-alkenes (principally, 1-hexene). A second system, involving TiCl 4 /alkylaluminum halide, also gave hyperbranched polyethene, with a ratio of methyl hydrogens/total alkyl hydrogens of 0.10-0.25. Weightaverage molecular weights varied from 900 to 1800 daltons. Higher selectivity to liquid product was achieved through the addition of dihydrogen. The mechanism of the formation of branched polyethene appears to involve, for the most part, oligomerization of ethene to 1-alkenes (principally 1-hexene) by a transition metal alkyl species followed by cationic oligomerization of the 1-alkenes by Lewis acidic species. The addition of tetraalkylammonium chloride to the TaCl 5 /Et 3 Al system resulted in a change in product selectivity from all polyethene to >65% 1-hexene. The highly selective trimerization of ethene by the tantalum system is unusual.An important goal in the polymerization of alkenes is the synthesis of low molecular weight (ca. 500-5000 daltons) hyperbranched polymers from inexpensive monomers such as ethene and propene. Such polymers are useful in the lubricant industry as base stocks and precursors to lubricant additives. Indeed, the demand for synthetic lubricant materials is rising. 1 Almost half of all synthetic lubricant base stocks are polymers of higher 1-alkenes, usually 1-decene. Despite the increasing demand for synthetic lubricants, 1-alkene capacity has not increased significantly. The advent of a lubricant material synthesized directly from a plentiful and less expensive monomer such as ethene is, therefore, of great current interest.We have recently reported the synthesis of hyperbranched polymers from ethene using nickel and palladium catalysts. 2 The polymers synthesized had weight-average molecular weights (relative to polystyrene standards) ranging from 400 to 1100 daltons and ratios of methyl hydrogens to total aliphatic hydrogens (H Me /H tot , obtained from integration of 1 H NMR spectra) from 0.4 to 0.65 (H Me /H tot ) 0 for totally linear polyethene). However, the reactions catalyzed by nickel compounds were highly exothermic, and both the nickel and palladium catalysts produced a significant amount of butenes that essentially represented wasted monomer. Because of the higher tendency of late transition metal alkyls to undergo -hydrogen abstraction, we examined early transition metal compounds as possible catalysts for the synthesis of hyperbranched polyethene. The titanium-based synthesis of branched polymers from ethene has been reported previously; however, the detailed structures of the polymers and the reaction mechanism were not investigated. 3,4 Our catalytic systems...

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Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

et al. 2000

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“…The homogeneous Ziegler–Natta catalyst system, comprised of titanium (IV) alkoxides in association with trialkylaluminum, was originally considered for the production of high‐molecular‐weight polyethylene . These catalysts have repeatedly been the subject of the modification aiming at the selective production of dimeric and oligomeric products . Such processes struggle to meet the increasing market demand for short‐chained linear alpha olefins such as butene‐1, hexene‐1, and octene‐1, which are high value co‐monomers for the production of linear low‐density polyethylene …”

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Alkoxysilane modification of a Ti‐based catalyst system for ethylene dimerization: A step forward in enhancing productivity and selectivity

Bigdeli

Abdouss

Abedi

2016

J of Applied Polymer Sci

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Alkoxysilanes were used as novel enhancing agents in the Ti-based catalyst for the highly selective ethylene dimerization to butene-1. The dimerization of ethylene was carried out using the homogeneous Ti(OBu) 4 /THF/TEA/alkoxysilane catalyst system, where Ti(OBu) 4 , THF (tetrahydrofuran), TEA (triethylaluminum), and alkoxysilane were used as catalyst, additive, activator, and modifier, respectively. The nature and concentration of alkoxysilanes on the dimerization rate, catalyst yield, by-products production, and selectivity to butene-1 were investigated in detail. It was found that the performance of alkoxysilanes assisted with the class of the Ti-based catalyst system, developed in this work, has been furthered by high productivity and selectivity with respect to the bare catalyst system. It proved that alkoxysilanes could play an excellent improving role in the selective ethylene dimerization process. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44615.

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η ¹ σ‐Alkyl Complexes by Insertion of Monoolefins into σ‐Alkyl—, σ‐Aryk σ‐Vinyl‐, and σ‐Acyl‐Metal Bonds

Heck¹

1991

Inorganic Reactions and Methods

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Reactions of Olefins with the Titanium‐Carbon Bond

Abstract: At low temperatures, ethylene and u-olefins (hl-olefins or I-alkenes)

Cited by 28 publications

References 12 publications

Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

Alkoxysilane modification of a Ti‐based catalyst system for ethylene dimerization: A step forward in enhancing productivity and selectivity

η ¹ σ‐Alkyl Complexes by Insertion of Monoolefins into σ‐Alkyl—, σ‐Aryk σ‐Vinyl‐, and σ‐Acyl‐Metal Bonds

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Reactions of Olefins with the Titanium‐Carbon Bond

Abstract: At low temperatures, ethylene and u-olefins (hl-olefins or I-alkenes)

Cited by 28 publications

References 12 publications

Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

Tantalum- and Titanium-Based Catalytic Systems for the Synthesis of Hyperbranched Polyethene

Alkoxysilane modification of a Ti‐based catalyst system for ethylene dimerization: A step forward in enhancing productivity and selectivity

η 1 σ‐Alkyl Complexes by Insertion of Monoolefins into σ‐Alkyl—, σ‐Aryk σ‐Vinyl‐, and σ‐Acyl‐Metal Bonds

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η ¹ σ‐Alkyl Complexes by Insertion of Monoolefins into σ‐Alkyl—, σ‐Aryk σ‐Vinyl‐, and σ‐Acyl‐Metal Bonds