Kinetic Investigation of Ethylene/Norbornene Polymerization and Copolymerization Using Methylpalladium(II) Catalysts with α-Amino-Pyridine Ligands
Date Issued
2007
Date
2007
Author(s)
Tu, Chia-Chun
DOI
en-US
Abstract
The cationic organopalladium(II) complexes bearing the -amino-pyridine ligands have been found as active catalysts for olefin polymerization and copolymerization.
In this work, we studied two types of catalysts, the neutral [PdCl(LH)(Me)]) and cationic [Pd(LH)(Me)(MeCN)]+BF4
- wherein LH= (C5H4N)CH2NHtBu (1), (C5H4N)CH2NH (2,6-(CH3)2C6H3) (2). The identification for such isomers could be
readily established by the NMR techniques and X-ray crystallography. These species existed as asymmetric square planar geometry, so that there should be two geometric isomers, cis- form and trans- form, resulted. However, according to 1H NMR spectra of the cationic complex with ligand 1, the isomer of the cis- form in term of relative
position of the acetonitrile ligand and the pyridine moiety was negligible. Both neutral and cationic complexes showed good activity for polymerization of norbornene, the cationic species especially. To neutral complexes, the best activity was about 60 g/mole•hr, and it was around 4350 g/mole•hr to the cationic species. Nevertheless, there was the curious detection. The catalytic activity resulting from the cis- isomer was better than the trans- isomer.
Furthermore, the kinetics of ethylene/norbornene polymerization and copolymerization was investigated by electrospray ionization tandem mass spectrometry. The spectra showed that the amount of olefin insertion increased with time and the analysis revealed that in the polymerization of norbornene/ethylene, the anterior active
species was (LH)Pd-Me, and the posterior active center was (LH)Pd-H. On the other hand, the norbornene inserted species could be served as the leading role in the copolymerization of ethylene/norbornene. At the same time, we could find that there existed linearity between the rate
constant and the concentration of norbornene by means of kinetic equations from the data analysis. And the concentration of the additive, acetonitrile would thwart the
insertion of norbornene.
Subjects
胺基-吡
啶
烯烴聚合
共聚合
動力學
polymerization
copolymerization
amino-pyridine ligand
Type
thesis
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