Assessing the Scope of the Introduction of Schiff Bases as Co-Ligands for Monometallic and Homobimetallic Ruthenium Ring-Opening Metathesis Polymerisation and Ring-Closing Metathesis Initiators

A new class of homobimetallic and monometallic Schiff base-substituted ruthenium olefin metathesis catalysts has been prepared, characterised and tested in ring-closing metathesis (RCM) and ring-opening metathesis polymerisation (ROMP) reactions. The results obtained point out that the synergy of Schiff base ligands with coordinatively labile ligands leads to bimetallic catalytic systems that combine very high activity with excellent stability. Furthermore, the catalytic activity of these catalysts is very dependent on the steric and electronic environment of the Schiff base. To conclude, a mechanism that explains the obtained data is postulated.