The influence of perhydroazepine and piperidine as further ancillary ligands on Ru-PPh3-based catalysts for ROMP of norbornene and norbornadiene Original Research Article

Polynorbornadiene and polynorbornene were synthesized via ring opening metathesis polymerization (ROMP) with [RuCl2(PPh3)2(amine)] as catalyst precursors, amine = piperidine (1) or perhydroazepine (2) in the presence of 5 μL of ethyl diazoacetate (EDA) ([monomer]/[Ru] = 5000; 40 °C with 1; 25 °C with 2). The effects of the solvent volume (2–8 mL of CHCl3), reaction time (5–120 min) and atmosphere type (argon and air) on the yields were investigated to observe the behavior of the two different precursors. Quantitative yields were obtained for 60 or 120 min regardless of the starting volumes, either in argon or air, with both Ru species. However, low yields were obtained for short times (5–30 min) when the reactions are performed with large volumes (6–8 mL). In argon, the yields were larger with 2, associated to a faster propagation reaction controlled by the Ru active species. In air, the yields were larger with 1, associated to a higher resistance to O2 of the starting and propagating Ru species. The different activities between 1 and 2 are discussed considering the steric hindrance and electronic characteristics of the amines such as ancillary ligands and their arrangements with PPh3 and Cl− ions in the metal centers.