Syndioselective Ring-Opening Metathesis Polymerization of endo-Dicyclopentadiene with Tungsten Complexes Having Imido Ligands: Development of Crystalline Syndiotactic Hydrogenated Poly(endo-dicyclopentadiene)

Tungsten-based catalysts induced syndioselective ring-opening metathesis polymerization (ROMP) of endo -dicyclopentadiene (DCPD) to produce a new class of crystalline polymer. Various tungsten(VI) imido chloride complexes of the type W( N−R)Cl 4 ·(Et 2 O) n (R = Ph, 2,6-Me 2 Ph, α-naphthyl, 2,6- i -Pr 2 Ph, Et, n -Bu, n -Hex, cyclohexyl, adamantyl; n = 0 or 1) were prepared, which in combination with Et 2 Al(OEt) efficiently induced ROMP of DCPD. W( N−Ph)Cl 4 ·Et 2 O and W( N−Et)Cl 4 ·Et 2 O promoted cis - and syndioselective ROMP of DCPD, and the following hydrogenation provided a new crystalline polymer, syndiotactic hydrogenated poly(DCPD), which was characteristic in high melting point and in high crystallinity ( T m = 270 °C, Δ H = 52 J/g, w c = 0.61). The syndioselectivity of the polymerization could be controlled in the range 30−80% by the suitable choice of those tungsten imido catalysts. These are the first examples of well-designed binary catalysts that are effective in the syndioselective ROMP of DCPD.