Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anion

Fuquan Song; Mark D. Hannant; Roderick D. Cannon; Manfred Bochmann

doi:10.1002/masy.200450917

Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anion

Fuquan Song
, Mark D. Hannant
, Roderick D. Cannon
, Manfred Bochmann

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

36 Citations (Scopus)

Abstract

The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr₃)₂]^- have been quantified (Z = CN, NH₂, N(CN)₂; Ar = C₆F₅ or o-C₆F₄C₆F₅). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl₂ have been determined using quenched-flow kinetic and batch techniques [SBI = rac-Me₂Si(1-Ind)₂]. Comparison of two activator systems, (i) CPh₃[B(C₆F₅)₄] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (I_a) mechanism is proposed.

Original language	English
Pages (from-to)	173-186
Number of pages	14
Journal	Macromolecular Symposia
Volume	213
Issue number	1
DOIs	https://doi.org/10.1002/masy.200450917
Publication status	Published - 29 Jun 2004

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title = "Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anion",

abstract = "The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr3)2]- have been quantified (Z = CN, NH2, N(CN)2; Ar = C6F5 or o-C6F4C6F5). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl2 have been determined using quenched-flow kinetic and batch techniques [SBI = rac-Me2Si(1-Ind)2]. Comparison of two activator systems, (i) CPh3[B(C6F5)4] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (Ia) mechanism is proposed.",

author = "Fuquan Song and Hannant, \{Mark D.\} and Cannon, \{Roderick D.\} and Manfred Bochmann",

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T1 - Zirconocene-catalysed propene polymerisation: kinetics, mechanism, and the role of the anion

AU - Song, Fuquan

AU - Hannant, Mark D.

AU - Cannon, Roderick D.

AU - Bochmann, Manfred

PY - 2004/6/29

Y1 - 2004/6/29

N2 - The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr3)2]- have been quantified (Z = CN, NH2, N(CN)2; Ar = C6F5 or o-C6F4C6F5). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl2 have been determined using quenched-flow kinetic and batch techniques [SBI = rac-Me2Si(1-Ind)2]. Comparison of two activator systems, (i) CPh3[B(C6F5)4] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (Ia) mechanism is proposed.

AB - The olefin polymerisation activity of metallocene catalysts strongly depends on the counteranion provided by the activator system. The relative activities of a number of new diborate anions [Z(BAr3)2]- have been quantified (Z = CN, NH2, N(CN)2; Ar = C6F5 or o-C6F4C6F5). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl2 have been determined using quenched-flow kinetic and batch techniques [SBI = rac-Me2Si(1-Ind)2]. Comparison of two activator systems, (i) CPh3[B(C6F5)4] / triisobutylaluminium (TIBA) and (ii) methylaluminoxane (MAO) shows, surprisingly, that the concentration of species actively involved in chain growth at any one time is comparable for both systems, although the MAO-activated catalyst is about 20 times less active than the borate system. It is concluded that the counteranion remains sufficiently strongly bound to the metal centre throughout the chain growth sequence to modulate the energetics of monomer insertion. A model suggesting that the monomer binding follows an associative interchange (Ia) mechanism is proposed.

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DO - 10.1002/masy.200450917

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