Latent Ruthenium Olefin Metathesis Catalysts That Contain an N-Heterocyclic Carbene Ligand

Abstract

A new N-heterocyclic carbene containing olefin metathesis catalyst, (sIMes)(Cl) 2 Ru(CH(CH 2 ) 2 - C, N -2-C 5 H 4 N) ( 4a ), was synthesized from (sIMes)(PCy 3 )(Cl) 2 Ru CHPh ( 1 ) or (sIMes)(py) 2 (Cl) 2 Ru CHPh ( 3 ). When heated at 40 °C in dichloromethane, 4a is slowly converted to its isomer 4b . The X-ray structures of 4a and 4b show that the NHC and pyridine ligands are trans in 4a and cis in 4b . 4a is more latent than 1 and 4b much more latent than 4a in ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP).