Syntheses of Various (Arylimido)vanadium(V)–Dialkyl Complexes Containing Aryloxo and Alkoxo Ligands, and Ring-Opening Metathesis Polymerization Using a Vanadium(V)–Alkylidene Complex

Treatment of V(NAr)(CH 2 SiMe 3 ) 3 ( 1, Ar = 2,6-Me 2 C 6 H 3 ) with 1.0 equiv of various alcohols in n -hexane at 25 °C cleanly afforded the corresponding dialkyl complexes of the type V(NAr)(CH 2 SMe 3 ) 2 (OR) [R = 2,6-Me 2 C 6 H 3 ( 2a ), 2,6- i Pr 2 C 6 H 3 ( 2b ), C 6 F 5 ( 2c ), t Bu ( 2d ), CMe(CF 3 ) 2 ( 2e ), yield 90−93%]. In contrast, the reactions with R′N(H)Me (R′ = Ph, cyclohexyl) or 2,6-Me 2 C 6 H 3 SH did not take place even if the reactions were attempted in C 2 D 2 Cl 4 at 50 °C. Complexes 2a and 2b showed high catalytic activities for the ring-opening metathesis polymerization (ROMP) of norbornene in the presence of PMe 3, and the activity increased at high temperature (80 °C). A vanadium(V)−alkylidene complex, V(CHSiMe 3 )(NAr)(O-2,6- i Pr 2 C 6 H 3 )(PMe 3 ) x ( 3, x = 0.89), has been isolated when the C 6 D 6 solution containing 2b was heated at 80 °C in the presence of PMe 3 (5.0 equiv). Complex 3 showed remarkable catalytic activity for the ROMP of norbornene, and the polymerization at 25 °C proceeded in a living manner.