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Zirconocene‐catalysed propene polymerisation: kinetics, mechanism, and the role of the anion
Author(s) -
Song Fuquan,
Hannant Mark D.,
Can Roderick D.,
Bochmann Manfred
Publication year - 2004
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200450917
Subject(s) - methylaluminoxane , chemistry , propene , monomer , metallocene , catalysis , polymerization , ethylene , kinetics , polymer chemistry , metal , medicinal chemistry , reaction mechanism , stereochemistry , organic chemistry , physics , quantum mechanics , polymer
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(BAr 3 ) 2 ] − have been quantified (Z = CN, NH 2 , N(CN) 2 ; Ar = C 6 F 5 or o ‐C 6 F 4 C 6 F 5 ). The kinetic parameters for the initiation, propagation and termination steps of propene polymerisations catalysed by (SBI)ZrCl 2 have been determined using quenched‐flow kinetic and batch techniques [SBI = rac ‐Me 2 Si(1‐Ind) 2 ]. Comparison of two activator systems, (i) CPh 3 [B(C 6 F 5 ) 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.