Olefin-metathesis reactions using vinylideneruthenium(II) complexes as catalyst precursors

Vinylideneruthenium(II) complexes of the type RuCl2(CCHR)L2 (R=But, ferrocenyl; L=PPri3, PCy3), which are easily accessible from [RuCl2(p-cymene)]2 and terminal alkynes, have been found to serve as good catalyst precursors for ring-opening metathesis polymerization (ROMP) of cyclic alkenes and ring-closing metathesis (RCM) of α,ω-dienes, α,ω-enynes, and dienynes. These complexes possess high stability toward air and heat, compared with the metathesis-active alkylidenerutheniums. Molecular weight control of poly(norbornene) in extremely wide range (Mn/103=500–4) has been achieved by using heteroatom-substituted vinylic compounds such as ethyl vinyl ether and phenyl vinyl sulfide as chain-transfer agents for ROMP.