| Abstract: | This paper reports the structural modification of Hoveyda–Grubbs complexes through the introduction of either an N‐alkyl‐N′‐mesityl heterocyclic carbene, an N‐alkyl‐N′‐(2,6‐diisopropylphenyl) heterocyclic carbene, or an N‐alkyl‐N′‐alkyl heterocyclic carbene. The effect of the modified N‐heterocyclic carbene (NHC) ligand was investigated in representative ring‐opening metathesis polymerization (ROMP), ring‐closing metathesis (RCM) and cross metathesis (CM) reactions. A pronounced influence on both catalyst activity and selectivity was found to be exerted by the NHC amino substituents, which emphasizes that a rigorously selected steric environment is critical in olefin metathesis catalyst design. |
