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

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 (NH2sBu, 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.

Graphical abstractThe role of amines as ancillary ligands are discussed in the ROMP of norbornene with [RuCl2(PPh3)2(amine)x], where x = 1 or 2, at room temperature or 50 °C for 5 min. Figure optionsDownload full-size imageDownload as PowerPoint slide