Olefin metathesis catalysts bearing hemilabile NHC ligands: Effect of remote torsional strain on activity

A ruthenium olefin metathesis catalyst (C1-H) bearing a novel NHC ligand tethered by a labile ethoxy-pyridyl arm was synthesized and characterized. The initiation rate, kinetics, metathesis activity, and decomposition behavior were compared with its methylated derivative (C1-Me), showing that these two catalysts vary profoundly. We demonstrate the considerable influence of remote torsional strain on the catalytic activity and decomposition behavior of this ligand class – a feature that can be exploited for related systems.