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The effect of the amido substituent on polymer molecular weight in propene homopolymerisation by titanium cyclopentadienyl‐amide catalysts
Author(s) -
Sinnema PietJan,
Hessen Bart,
Teuben Jan H.
Publication year - 2000
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/1521-3927(20000601)21:9<562::aid-marc562>3.0.co;2-#
Subject(s) - substituent , cyclopentadienyl complex , propene , amide , catalysis , polymer chemistry , chemistry , depolymerization , polymer , titanium , organic chemistry
In the homopolymerisation of propene by the cyclopentadienyl‐amide titanium catalyst systems [η 5 ,η 1 ‐C 5 H 4 (CH 2 ) 2 NR]TiCl 2 /MAO and [η 5 ,η 1 ‐C 5 H 4 (CH 2 ) 2 NR]Ti(CH 2 Ph) 2 /B(C 6 F 5 ) 3 (R = t Bu, i Pr, Me), the catalyst with the smallest substituent (Me) on the amido moiety consistently gives the highest polymer molecular weight. This differs from the trend usually observed in related catalysts with tetramethylcyclopentadienyl‐amide ancillary ligands, where larger amide substituents result in higher molecular weights. Based on the present information a hypothesis is formulated in which an increased cation‐anion interaction for the less sterically hindered catalyst is responsible for disfavouring chain transfer relative to chain growth.