Abstract
Oligomeric vinyl polynorbornene (2 to ∼12 monomer units) was obtained via hydrooligomerization of norbornene (NB) using the cationic palladium complexes [Pd(PPh 3) n (NCCH 3) 4− n ](BF 4) 2 [ n = 0 ( 1), 3 ( 2)] at different hydrogen pressures. The vinyl polymerization of norbornene (NB) in the ionic liquid N-butyl- N-trimethylammonium bis(trifluoromethylsulfonyl)imide (BtMA +NTf 2 −) with [Pd(NCCH 3) 4](BF 4) 2 led to soluble polynorbornenes (with several hundred monomer units) at different temperatures and molar NB:Pd ratios. The norbornene derivative 5-vinyl-2-norbornene (VNB) was oligomerized in high yield with 1 in CH 3NO 2 primarily through the (endocyclic) norbornene double bond but also through both the norbornene and (exocyclic) vinyl double bond for about every second monomer (by 1H NMR). A 2D 1H, 13C-HSQC NMR analysis suggests a β-hydrogen elimination after insertion of a norbornene double bond as chain-termination mechanism. The conversion of NB or VNB increased with temperature and a lower NB:Pd and VNB:Pd ratio, respectively. The vinyl double bond in VNB slowed down the insertion rate drastically when compared with NB (activity decrease by a factor of 10 2).
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