Synthesis of (Imido)niobium(V)-Alkylidene Complexes That Exhibit High Catalytic Activities for Metathesis Polymerization of Cyclic Olefins and Internal Alkynes

摘要

The (imido)niobium(V)-alkylidene complexes Nb(CHSiMe3)(NR)[OC(CF3)(3)](PMe3)(2) (R = 2,6-Me2C6H3, 2,6-'Pr2C6H3, 1-adamantyl), which could be isolated from the dialkyl analogues by a-hydrogen elimination in the presence of PMe3, exhibited remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene, and the polymerizations proceeded in a living manner. Metathesis polymerizations of (unstrained) disubstituted acetylenes also took place, affording polymers with uniform (narrow) molecular weight distributions.