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Analyses of Propene and 1‐Hexene Oligomers from Zirconocene/MAO Catalysts – Mechanistic Implications by NMR, SEC, and MALDI‐TOF MS
Author(s) -
Janiak Christoph,
Lange Katharina C. H.,
Marquardt Peter,
Krüger RalphPeter,
Hanselmann Ralf
Publication year - 2002
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20020101)203:1<129::aid-macp129>3.0.co;2-c
Subject(s) - propene , chemistry , double bond , oligomer , hexene , 1 hexene , catalysis , polymer chemistry , metallocene , proton nmr , stereochemistry , organic chemistry , polymerization , ethylene , polymer
A series of Cp′(C 5 H 5 )ZrCl 2 and Cp′ 2 ZrCl 2 pre‐catalysts (Cp′ = C 5 HMe 4 , C 4 Me 4 P, C 5 Me 5 , C 5 H 4 t Bu, C 5 H 3 ‐1,3‐ t Bu 2 , C 5 H 2 ‐1,2,4‐ t Bu 3 ) together with (C 5 H 5 ) 2 ZrCl 2 was used for the directed oligomerization of propene and 1‐hexene in comparative experiments. Oligomer characterization was carried out by 1 H NMR, SEC (GPC), MALDI‐TOF MS, cryoscopy and Raman spectroscopy. From 1 H NMR the nature and relative ratio of the double‐bond end group is determined together with M̄ n if every oligomer molecule contains such a double‐bond end group. Normally vinylidene double bonds (from β‐hydrogen elimination) are found. From 1 H NMR and MALDI‐TOF MS also vinyl end groups (from β‐methyl elimination) are observed in the case of oligopropenes with (C 4 Me 4 P)‐ (C 5 H 5 )ZrCl 2 and with the symmetrical methyl containing Cp′ 2 ZrCl 2 pre‐catalysts. The vinylidene/vinyl ratio depends on the ligand and increases from C 5 HMe 4 (65/35) over C 4 Me 4 P (61/39) to C 5 Me 5 (9/91). A comparison of M̄ n from 1 H NMR and SEC together with MALDI‐TOF MS shows that the phospholyl‐zirconocenes and (C 5 HMe 4 ) 2 ZrCl 2 also exhibit chain transfer to aluminium, thereby giving saturated oligomers.