Norbornadiene homopolymerization and norbornene/norbornadiene/1-octene terpolymerization by ansa-fluorenylamidotitanium-based catalysts

ansa-Fluorenylamidotitanium complexes Me2Si(Flu)(NtBu)TiMe2 (1) and Me2Si(2,7-tBu2Flu)(NtBu)TiMe2 (2) were used as precatalysts for the homopolymerization of norbornadiene (NBD) and the terpolymerization of NBD, norbornene (NB), and 1-octene (OC). In the NBD homopolymerization, catalyst 2 showed double the conversion and yielded a polymer having more than double the molecular weight compared with catalyst 1 when activated by modified methylaluminoxane (MMAO). The conversion and molecular weight were significantly increased by changing the cocatalyst from MMAO to [Ph3C][B(C6F5)4]. The conversion levels after 10 min polymerization using 2-[Ph3C][B(C6F5)4] at 25 and 0 °C were 52% and 62%, respectively. The conversion reached 82% at 0 °C after 1 h, and soluble polyNBD with a number-average molecular weight (Mn) of 34 100 was obtained. The 2-[Ph3C][B(C6F5)4] catalytic system also showed the best performance for NBD/NB/OC terpolymerization among the four combinations of precatalyst/cocatalyst and gave the terpolymer with Mn of 66 300 containing 13 mol% of NBD at 64% conversion after 10 min polymerization at 0 °C. All resulting polymers possessed good solubility, indicating that crosslinking via the NB unit derived from NBD was negligible.