Reactivity of niobium(V) pentaalkoxide complexes: Ring-opening metathesis polymerization of norbornene

The ring-opening metathesis polymerization (ROMP) of cyclic olefins with niobium(V) pentaalkoxide catalysts was studied. In the presence of zinc, benzylidene dichloride, and chlorotrimethylsilane, in situ niobium species was formed and ROMP reaction proceeded. Among niobium pentaalkoxide group, Nb(OEt)5 achieved the smallest dispersity value of the polymer and provided trans selective polynorbornene. In this paper, we discussed the role of additives and expected how the polymer was synthesized with Nb(OEt)5/TMSCl/Zn/PhCHCl2 system. We also elucidated the intermediate using some measurement.