Synthesis of double-end-capped polyethylene by a cationic tris(pyrazolyl)borate zirconium benzyl complex

Katrin Nienkemper; Han Lee; Richard F. Jordan; Alireza Ariafard; Li Dang; Zhenyang Lin

doi:10.1021/om800558w

Synthesis of double-end-capped polyethylene by a cationic tris(pyrazolyl)borate zirconium benzyl complex

Katrin Nienkemper, Han Lee, Richard F. Jordan, Alireza Ariafard, Li Dang, Zhenyang Lin

Research School of Chemistry

Research output: Contribution to journal › Article › peer-review

25 Citations (Scopus)

Abstract

The cationic complexes Tp*Zr(CH₂Ph)₂ ⁺ (I, B(C₆F₅)₄^- salt; Tp* = HB(3,5-Me₂-pyrazolyl)₃) and {(PhCH ₂)(H)B(μ-Me₂pz)₂}Zr(η²- Me₂pz)(CH₂Ph)⁺ (II; Me₂pz = 3,5-Me₂-pyrazolyl) polymerize ethylene at -78 to -60°C to linear polyethylene (PE) without significant chain transfer. For I, chain growth takes place at only one benzyl group. Quenching these polymerizations with MeOH yields benzyl-capped PE (PhCH₂(CH₂CH₂) _nCH₂CH₃). Quenching I-catalyzed ethylene polymerization with Br₂ yields double-end-capped PE containing benzyl and bromo chain ends (PhCH₂(CH₂CH₂) _nCH₂CH₂Br). DFT calculations on model catalysts show that ethylene insertion into a Zr-η²-CH₂Ph bond requires greater structural distortion than insertion into a Zr-CH ₂CH₂CH₂Ph bond. The calculations also show that the β-H transfer to monomer and β-H elimination chain transfer pathways are both strongly disfavored for I, but the β-H transfer to monomer path may be possible for II.

Original language	English
Pages (from-to)	5867-5875
Number of pages	9
Journal	Organometallics
Volume	27
Issue number	22
DOIs	https://doi.org/10.1021/om800558w
Publication status	Published - 24 Nov 2008

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@article{5860b97a3bc149608c6539f16940d212,

title = "Synthesis of double-end-capped polyethylene by a cationic tris(pyrazolyl)borate zirconium benzyl complex",

abstract = "The cationic complexes Tp*Zr(CH2Ph)2 + (I, B(C6F5)4- salt; Tp* = HB(3,5-Me2-pyrazolyl)3) and {(PhCH 2)(H)B(μ-Me2pz)2}Zr(η2- Me2pz)(CH2Ph)+ (II; Me2pz = 3,5-Me2-pyrazolyl) polymerize ethylene at -78 to -60°C to linear polyethylene (PE) without significant chain transfer. For I, chain growth takes place at only one benzyl group. Quenching these polymerizations with MeOH yields benzyl-capped PE (PhCH2(CH2CH2) nCH2CH3). Quenching I-catalyzed ethylene polymerization with Br2 yields double-end-capped PE containing benzyl and bromo chain ends (PhCH2(CH2CH2) nCH2CH2Br). DFT calculations on model catalysts show that ethylene insertion into a Zr-η2-CH2Ph bond requires greater structural distortion than insertion into a Zr-CH 2CH2CH2Ph bond. The calculations also show that the β-H transfer to monomer and β-H elimination chain transfer pathways are both strongly disfavored for I, but the β-H transfer to monomer path may be possible for II.",

author = "Katrin Nienkemper and Han Lee and Jordan, {Richard F.} and Alireza Ariafard and Li Dang and Zhenyang Lin",

year = "2008",

month = nov,

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doi = "10.1021/om800558w",

language = "English",

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T1 - Synthesis of double-end-capped polyethylene by a cationic tris(pyrazolyl)borate zirconium benzyl complex

AU - Nienkemper, Katrin

AU - Lee, Han

AU - Jordan, Richard F.

AU - Ariafard, Alireza

AU - Dang, Li

AU - Lin, Zhenyang

PY - 2008/11/24

Y1 - 2008/11/24

N2 - The cationic complexes Tp*Zr(CH2Ph)2 + (I, B(C6F5)4- salt; Tp* = HB(3,5-Me2-pyrazolyl)3) and {(PhCH 2)(H)B(μ-Me2pz)2}Zr(η2- Me2pz)(CH2Ph)+ (II; Me2pz = 3,5-Me2-pyrazolyl) polymerize ethylene at -78 to -60°C to linear polyethylene (PE) without significant chain transfer. For I, chain growth takes place at only one benzyl group. Quenching these polymerizations with MeOH yields benzyl-capped PE (PhCH2(CH2CH2) nCH2CH3). Quenching I-catalyzed ethylene polymerization with Br2 yields double-end-capped PE containing benzyl and bromo chain ends (PhCH2(CH2CH2) nCH2CH2Br). DFT calculations on model catalysts show that ethylene insertion into a Zr-η2-CH2Ph bond requires greater structural distortion than insertion into a Zr-CH 2CH2CH2Ph bond. The calculations also show that the β-H transfer to monomer and β-H elimination chain transfer pathways are both strongly disfavored for I, but the β-H transfer to monomer path may be possible for II.

AB - The cationic complexes Tp*Zr(CH2Ph)2 + (I, B(C6F5)4- salt; Tp* = HB(3,5-Me2-pyrazolyl)3) and {(PhCH 2)(H)B(μ-Me2pz)2}Zr(η2- Me2pz)(CH2Ph)+ (II; Me2pz = 3,5-Me2-pyrazolyl) polymerize ethylene at -78 to -60°C to linear polyethylene (PE) without significant chain transfer. For I, chain growth takes place at only one benzyl group. Quenching these polymerizations with MeOH yields benzyl-capped PE (PhCH2(CH2CH2) nCH2CH3). Quenching I-catalyzed ethylene polymerization with Br2 yields double-end-capped PE containing benzyl and bromo chain ends (PhCH2(CH2CH2) nCH2CH2Br). DFT calculations on model catalysts show that ethylene insertion into a Zr-η2-CH2Ph bond requires greater structural distortion than insertion into a Zr-CH 2CH2CH2Ph bond. The calculations also show that the β-H transfer to monomer and β-H elimination chain transfer pathways are both strongly disfavored for I, but the β-H transfer to monomer path may be possible for II.

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U2 - 10.1021/om800558w

DO - 10.1021/om800558w

M3 - Article

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JO - Organometallics

JF - Organometallics

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ER -

Synthesis of double-end-capped polyethylene by a cationic tris(pyrazolyl)borate zirconium benzyl complex

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