Latent cationic palladium(II) phosphine carboxylate complexes for norbornene polymerization

The catalytic efficacy of trans-[(R3P)2Pd(O2CR′)(LB)][B(C6F5)4] (1) (LB = Lewis base) and [(R3P)2Pd(κ2-O,O-O2CR′)][B(C6F5)4] (2) for mass polymerization of 5-n-butyl-2-norbornene (Butyl-NB) was investigated. The nature of PR3 and LB in 1 and 2 are the most critical components influencing catalytic activity/latency for the mass polymerization of Butyl-NB. Further, it was shown that 1 is in general more latent than 2 in mass polymerization of Butyl-NB. 5-n-Decyl-2-norbornene (Decyl-NB) was subjected to solution polymerization in toluene at 63(±3) °C in the presence of several of the aforementioned palladium complexes as catalysts and the polymers obtained were characterized by gel permeation chromatography. Cationic trans-[(R3P)2PdMe(MeCN)][B(C6F5)4] [R = Cy (3a), and iPr (3b)] and trans-[(R3P)2PdH (MeCN)][B(C6F5)4] [R = Cy (4a), and iPr (4b)], possible products from thermolysis of trans-[(R3P)2Pd(O2CMe)(MeCN)][B(C6F5)4] [R = Cy (1a) and iPr (1g)], as well as trans-[(R3P)2Pd(η3-C3H5)][B(C6F5)4] [R = Cy (5a), and iPr (5b)], were also examined as catalysts for solution polymerization of Decyl-NB. A maximum activity of 5360 kg/(molPd h) of 2a was achieved at a Decyl-NB/Pd: 26,700 ratio which is slightly better than that achieved with 5a [activity: 5030 kg/(molPd h)] but far less compared with 4a [activity: 6110 kg/(molPd h)]. Polydispersity values indicate a single highly homogeneous character of the active catalyst species. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 103–110, 2009