Highly Active Metathesis Catalysts Generated In Situ from Inexpensive and Air-Stable Precursors

Ruthenium vinylidenes: metathesis catalysis on the bench? Ruthenium vinylidene compounds 1, generated in situ from readily available, air-stable precursors, are used to catalyze ring-closing metathesis, ene–yne metathesis, cross-metathesis, and ring-opening metathesis polymerization. Bulky imidazolylidene ligands and terminal alkynes were found to be necessary components for achieving high catalytic activity.