Ruthenium and osmium metal carbene complexes for olefin metathesis polymerization

In the process of metathesis polymerization of cyclic olefins, the improvement comprising carrying out the polymerization in the presence of a catalyst of the formula ##STR35## in the presence of a solvent, wherein:

• M is Os or Ru;
• R and R.sup.1 are independently selected from hydrogen;
• C.sub.1 -C.sub.20 alkyl, C.sub.2 -C.sub.20 alkenyl, C.sub.2 -C.sub.20 alkynyl, C.sub.2 -C.sub.20 alkoxycarbonyl, aryl, C.sub.1 -C.sub.20 carboxylate, C.sub.1 -C.sub.20 alkoxy, C.sub.2 -C.sub.20 alkenyloxy, C.sub.2 -C.sub.20 alkynyloxy or aryloxy;
• each optionally substituted with C.sub.1 -C.sub.5 alkyl, halogen, C.sub.1 -C.sub.6 alkoxy or with a phenyl group substituted with halogen, C.sub.1 -C.sub.5 alkyl or C.sub.1 -C.sub.5 alkoxy;
• X and X.sup.1 are independently selected from an anionic ligand;
• and
• L and L.sup.1 are independently selected from neutral electron donor.