Activation of ruthenium based catalyst compounds with acid to improve reaction rates and yields of olefin metathesis reactions, including ROMP, RCM, ADMET and cross-methasis reactions is disclosed. The ruthenium catalyst compounds are ruthenium carbene complexes of the general formula A.sub.x L.sub.y X.sub.z Ru.dbd.CHR' where x=0, 1 or 2, y=0, 1 or 2, and z=1 or 2 and where R' is hydrogen or a substituted or unsubstituted alkyl or aryl, L is any neutral electron donor, X is any anionic ligand, and A is a ligand having a covalent structure connecting a neutral electron donor and an anionic ligand. The use of acid with these catalysts allows for reactions with a wide range of olefins in a variety of solvents, including acid-initiated RIM processes and living ROMP reactions of water-soluble monomers in water.