Two new ruthenium complexes bearing a bidentate (κ(2)O,C)-isopropoxy-indenylidene ligand and a PPh(3) (9) or PCy(3) (10, Cy=cyclohexyl) ligand have been synthesized and fully characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography. Complex 10 displays a very high thermal stability with a half life of six days at 110 °C in [D(8)]toluene. Complex 10 was evaluated in various ring-closing metathesis reactions and ring-opening metathesis polymerization of dicyclopentadiene, in which it showed a latent behavior with low activity at room temperature and high activity upon thermal activation.