Solvent-Free Ring-Opening Metathesis Polymerization of Norbornene over Silica-Supported Tungsten-Oxo Perhydrocarbyl Catalysts

Ring opening metathesis polymerization (ROMP) of bicyclo[2.2.1]hept‐2‐ene (norbornene) is carried out over silica‐supported catalysts based on tungsten complexes bearing an oxo ligand (1: [(SiO)W(O)(CH2SiMe3)3, 2: [(SiO)W(O)(CHCMe2Ph)(dAdPO)], dAdPO  2,6 diadamantyl‐4‐methylphenoxide, 3: [(SiO)2W(O)(CH2SiMe3)2]). The evaluation of the catalytic activities of the aforementioned materials in ROMP indicates that at low reaction time (0.5 min), the highest polymer yield is obtained with catalyst 2. However, for longer reaction time (>2 min), complex 3, a model of the industrial catalyst, exhibits a better monomer conversion. The polymers obtained are characterized. Moreover, these catalysts are shown to be rather preferentially selective to give the cis polynorbornene (>65%), characterized by high melting points (≈300 °C). The experimental values of the average molecular weight (Mn) of polynorbornenes are found to be close to the theoretical ones for the polymers prepared using catalyst 2 and higher for those originated from catalyst 3. Catalytic activities of well‐defined silica‐supported tungsten–oxo complexes, prepared via surface organometallic chemistry, are evaluated in ring opening metathesis polymerization of norbornene. [(SiO)2W(O)(CH2SiMe3)2], a model of the industrial catalyst, shows the best catalytic performances. Its activity is five times higher compared to the one measured in the presence of toluene. In addition, this material leads to a better control of the polydispersity.