Synthesis of Alumina-Terminated Linear PE with a Hafnium Aminopyridinate Catalyst

Haas, Isabelle; Kretschmer, Winfried P.; Kempe, Rhett

doi:10.1021/om200355q

Cited by 30 publications

(41 citation statements)

References 52 publications

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“…Fig. 18) [31]. The main purpose for the synthesis of these complexes was their application in ethylene polymerization and coordinative chain transfer polymerization (CCTP).…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

“…The polymers obtained in this polymerization possess contain a main group metal at one end of the chain which could be further functionalized to get valuable products. For example, this polymerization affords long-chain aluminum alkyls which upon oxidation could be converted into long-chain aliphatic alcohols [31]. These alcohols have wide range of applications such as in metal/polymer/leather processing, in paints and industrial coating materials.…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

“…Hf-complexes (68)(69)(70)(71)(72) were employed for ethylene polymerization using MAO as co-catalyst [31]. Catalyst 68 was active for ethylene polymerization with polydispersity index less than 2, whereas catalysts 69-72 were not active under the applied conditions (50°C, 15 min reaction time); however; they were more active on increasing temperature and reaction time plausibly because, reaction time and temperature speeds up the reaction between catalyst and MAO which is beneficial for activity enhancement [31].…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

“…In previous studies, Kempe et al have reported the application of yttrium aminopyridinato complexes for CCTP and obtained aluminum- with lower polydispersity index (1.4). In following studies, Kempe et al have employed complexes 68-72 for ethylene polymerization studies, and only complex 68 has shown good activity, and this complex was subjected to CCTP using triethyl aluminum as chain transfer agent, and the effect of different parameters such as temperature, catalyst/ CTA ratio, ethylene pressure and reaction time has been investigated [31]. The activity of the complex 68 was low at 50°C and 2 bar ethylene pressure but increased to 1960 kg mol cat -1 h -1 when activated with ammonium borate at 80°C, but the resultant polymer had a broader molecular weight distribution.…”

Section: Coordinative Chain Transfer Polymerization (Cctp) By Complex 68mentioning

confidence: 99%

“…It has been noticed that resulting polymer gets precipitated out during the reaction which inhibits the chain transfer rate; however, it can be overcome by increasing the temperature [55b]. Also, a bimodal distribution and substantial amount of precipitated polymer was found [31]. Higher pressure has a pronounced effect on activity, molecular weight and polydispersity.…”

Section: Coordinative Chain Transfer Polymerization (Cctp) By Complex 68mentioning

confidence: 99%

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Aminopyridine stabilized group-IV metal complexes and their applications

Hafeez

Muhammad

2016

Appl Petrochem Res

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During the last two decades, group-IV metalsbased aminopyridinato complexes have attracted a tremendous research interest because of immense industrial needs for the catalyst which would be of higher activity and selectivity with lower toxicity and lower cost. Chemistry of titanium (Ti) and zirconium (Zr) complexes was more extensively explored as compared to hafnium (Hf) complexes. Direct synthesis, salt metathesis, amine elimination, alkane elimination, silyl chloride elimination, hydrogen chloride elimination and toluene elimination protocols have been used for the synthesis of group-IV metal complexes. Changes in ligand and complex design were made to optimize these catalysts for olefin polymerization. Most of these complexes have shown good catalytic activities when activated with dry methyl aluminoxane. Ligand transfer to aluminum was found in these complexes, particularly with less bulky ligands, and this ligand transfer problem was overcome by tridentate ligands but the activities of these complexes were not competitive to complexes with bidentate aminopyridinato ligands. Majority of these complexes produce high-molecularweight polymers with broader molecular weight distributions, and Hf-complexes produce longer chain polymers than their comparative Ti and Zr aminopyridinato complexes. It could be deduced that group-IV metals inherit the potential for optimal polymerizing catalysts probably, because of their almost vacant d-orbitals, these act as hard acids which on combination with soft bases carry the opportunity to design and develop polymerization catalysts which could overcome the problems associated with existing systems.

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“…Fig. 18) [31]. The main purpose for the synthesis of these complexes was their application in ethylene polymerization and coordinative chain transfer polymerization (CCTP).…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

Section: Coordinative Chain Transfer Polymerization (Cctp) By Complex 68mentioning

confidence: 99%

Section: Coordinative Chain Transfer Polymerization (Cctp) By Complex 68mentioning

confidence: 99%

See 3 more Smart Citations

Aminopyridine stabilized group-IV metal complexes and their applications

Hafeez

Muhammad

2016

Appl Petrochem Res

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Zirconium complexes bearing bis(phenoxy‐imine) ligands with bulky o‐bis(aryl)methyl‐substituted aniline groups: synthesis, characterization and ethylene polymerization behavior

Huang

2013

Applied Organom Chemis

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A series of bis(phenoxy-imine) zirconium complexes bearing bulky o-bis(aryl)methyl-substituted aryl groups on the aniline moiety have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. 1 H NMR spectroscopy suggests that these complexes exist as a single chiral C 2 -symmetric isomer in the solution. X-ray crystallographic analysis of the resulting biszwitterionic-type adduct complex C1 Á 2HCl reveals that the phenoxy-imine groups function as a monodentate phenoxy ligand and the oxygen atoms are oriented trans to each other at the central metal atom. Using modified methylaluminoxane (MMAO) as co-catalyst, C1 Á 2HCl, C2-C6 exclusively produce linear aluminium-terminated polyethylenes (Al-PEs) with high activity (up to 16.89 Â 10 6 g PE (mol Zr h) À1 , suggesting that chain transfer to aluminum is the predominant termination mechanism. It is noteworthy that the introduction of an excessively bulky o-bis(aryl)methyl substituent adjacent to the imine-N produces low molecular-weight Al-PEs (M v 1.6-10.1 Â 10 3 ) due to the enhanced rate of chain transfer to alkylaluminium groups during polymerization.

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Polymerization via Insertion of Ethylene into Al−C bond under Mild Conditions: Mechanistic Studies on the Promotion Exerted by a Catalytic Amount of Cationic Gadolinium Metallocene

Fukushima

Tardif

Kaita

et al. 2021

Chemistry An Asian Journal

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The cationic gadolinium metallocene [(C 5 Me 5 ) 2 Gd][B(C 6 F 5 ) 4 ], when combined with an excess amount of Al( i Bu) 3 , efficiently produces polyethylene at 80°C under 0.8 MPa pressure of ethylene. After quenching, the resulting polyethylene has ethyl group at one end and isobutyl group at the other terminal. Because no Gd-alkyl species appears to be involved, a mechanism with conventional coordinative chain transfer polymerization (CCTP) is not feasible. Density functional theory (DFT) analyses indicate a novel mechanism in which the cationic Gd plays a crucial role by coordinating ethylene and assists the insertion of the coordinated ethylene into AlÀ C bond.

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Synthesis of Alumina-Terminated Linear PE with a Hafnium Aminopyridinate Catalyst

Cited by 30 publications

References 52 publications

Aminopyridine stabilized group-IV metal complexes and their applications

Aminopyridine stabilized group-IV metal complexes and their applications

Zirconium complexes bearing bis(phenoxy‐imine) ligands with bulky o‐bis(aryl)methyl‐substituted aniline groups: synthesis, characterization and ethylene polymerization behavior

Polymerization via Insertion of Ethylene into Al−C bond under Mild Conditions: Mechanistic Studies on the Promotion Exerted by a Catalytic Amount of Cationic Gadolinium Metallocene

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