(Arylimido)vanadium(V)–Alkylidene Complexes Containing Fluorinated Aryloxo and Alkoxo Ligands for Fast Living Ring-Opening Metathesis Polymerization (ROMP) and Highly Cis -Specific ROMP

(Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe3)(N-2,6-X2C6H3)(OC6F5)(PMe3)2 [X = Me (2), Cl (4)], exhibited remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene, and the ROMP by 2 proceeded in a living manner, affording ultrahigh molecular weight polymers. Cis-specific ROMP was achieved with the alkoxo analogues, V(CHSiMe3)(N-2,6-X2C6H3)[OC(CH3)(CF3)2]-(PMe3)2 [X = Me (5), Cl (6)]. Both the activity and the selectivity increased upon addition of PMe3, even at 50 °C.