Ring-opening polymerisation of norbornene by (μ-H)2Os3(CO)10 complex

The (μ-H)2Os3(CO)10 catalyses the ring opening polymerisation of norbornene to give high molecular weight poly (1,3-cyclopentylene-vinylene) in high yield. Initially IR and 13C-NMR data reveal the presence of an all cis structure of the polymer, whereas for longer reaction times there is a progressive increase in the trans content. A reaction mechanism for the polymerisation is proposed involving the formation of a dimetallacyclopentene intermediate.