Ring Opening Metathesis Polymerization (ROMP) of Norbornenes by (Arylimido)Niobium(V)–Alkylidene Catalysts, Nb(CHSiMe<sub>3</sub>)(NAr)[OC(CF<sub>3</sub>)<sub>3</sub>](PMe<sub>3</sub>)<sub>2</sub>
Kanchana Chatchaipaiboon, Kotohiro Nomura
Abstract
Effects of arylimido ligands on the ring-opening metathesis polymerization (ROMP) of norbornene (NBE), norbornadiene (NBD), and tetracyclododecene (TCD) were investigated using a series of (arylimido)niobium(V)–alkylidene complex catalysts, Nb(CHSiMe3)(NAr)[OC(CF3)3](PMe3)2 [Ar = 2,6-Me2C6H3 (1), 2-MeC6H4 (2), 2,6-Cl2C6H3 (3)]. The catalytic activity in ROMP of NBE for 1 was higher than for 2 and 3 (toluene at 25 °C, initial NBE concentration 0.44 mmol/mL), and the activity increased at 50 °C. Further increase in the activity (TOF 236 s–1) was observed using 3 with addition of 1.0 equiv. of PMe3, and activity was higher than that for the analogous vanadium(V)–alkylidene. These complexes (1-3) could also catalyze ROMP of NBD and TCD and the activities were higher than that for the ROMP of NBE. The dichlorophenylimido analogue (3) showed the highest activity for the ROMP of TCD, whereas 1 showed higher activity than 2 and 3 for the ROMP of NBD.