Acyclic amines as ancillary ligands in Ru-based catalysts for ring-opening metathesis polymerization. Probing the electronic and steric aspects of cyclic and acyclic amines

Article abstract of DOI:10.1016/j.molcata.2006.06.041

The present paper reports the ROMP of norbornene with [RuCl₂(PPh₃)₂(L)_x], where L represents the acyclic amines diethanolamine, triethanolamine, triethylamine, phenylamine, diphenylamine or sec-butylamine. Previous representative results with cyclic amines are also cited to observe of the behavior of cyclic and acyclic amines as ancillary ligands. Three productive types of ligands were observed as a function of their electronic nature and steric hindrance: ligands with high cone angle and strong σ-donor character (NH₂^sBu, NEt₃ and piperidine), ligands with high cone angle and low σ-donor character (NH₂Ph and NHPh₂) and ligand with low cone angle and π-acceptor character (4-H₂NC(O)-pyridine). Ligands with low cone angle and strong σ-donor character can restrict the catalytic activity of the metal complex (imidazole, pyridine, 4-H₃C-pyridine and 4-H₂N-pyridine). Thus, latent complexes can be designed using different amines as ancillary ligands.