Ring-Opening Polymerization of THF by Aryloxo-Modified (Imido)vanadium(V)-alkyl Complexes and Ring-Opening Metathesis Polymerization by Highly Active V(CHSiMe3)(NAd)(OC6F5)(PMe3)2

Ring-opening polymerizations of THF using V(NR)(CH2SiMe3)(OAr)(2) [R = 2,6-Me2C6H3, 1-adamantyl (Ad), Ph; Ar = 2,6-Me2C6H3, C6F5] proceeded in a living manner in the presence of [Ph3C][B(C6F5)(4)], affording high molecular weight polymers with low PDI (M-w/M-n) values: the observed activity (initiation efficiency) was affected by the arylimido and aryloxo ligands employed. A new vanadium(V)-alkylidene, V(CHSiMe3)(NAd)(OC6F5)(PMe3)(2), prepared from V(NAd)(CH2SiMe3)(2)(OC6F5) by alpha-hydrogen elimination in n-hexane in the presence of PMe3 at 25 degrees C, exhibited remarkable catalytic activity for ring-opening metathesis polymerization of norbornene: the activity at 25 degrees C was higher than those by the reported vanadium(V)-alkylidenes and ordinary Mo(CHCMe2Ph)(N-2,6-Pr-i(2)-C6H3)((OBu)-Bu-t)(2).