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

High Resolution Image Download MS PowerPoint Slide The (imido)niobium(V)–alkylidene complexes Nb(CHSiMe 3 )(NR)[OC(CF 3 ) 3 ](PMe 3 ) 2 (R = 2,6-Me 2 C 6 H 3, 2,6- i Pr 2 C 6 H 3, 1-adamantyl), which could be isolated from the dialkyl analogues by α-hydrogen elimination in the presence of PMe 3, 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.