Abstract: The present invention relates to a process for preparing polymers by means of ring-opening metathetic polymerization, consisting of the following steps: a) providing a reaction mixture consisting of a cycloalkene or a cycloalkene mixture, b) adding a ruthenium compound of the general formula RuX1X2L1aL2b (I) where a=0 or 1, b=1 or 2, such that a+b=2; X1, X2=independently selected anionic ligands; L1=uncharged ?-binding ligand; L2=N-heterocyclic carbene of the formula IIa, IIb or IIc; c) adding a chain transfer agent in a molar ratio in the range from 1:5 to 1:1000 based on the cycloalkene or the sum total of the cycloalkenes in the cycloalkene mixture, d) converting at a temperature within a range from 0° C. to 250° C.

Abstract: The present invention relates to a process for preparing olefins by means of metathesis, which comprises the following steps a. provision of an olefin reaction mixture containing at least one olefin, b. addition of a ruthenium compound of the general formula [RuX2L1xL2y]z (I), where X=anionic ligand; L1=uncharged ?-bonding ligand; L2=uncharged electron donor ligand; x=0, 1; y=1, 2, 3; z=1, 2, c. addition of a Lewis acid and/or an anionic, noncoordinating salt, d. reaction at temperatures in the range from 30° C. to 140° C., where no addition of an alkyne or alkynol is carried out. The invention further relates to the use of this process in metathesis reactions.

Abstract: The present invention relates to a process for preparing polymers by means of ring-opening metathetic polymerization, consisting of the following steps: a) providing a reaction mixture consisting of a cycloalkene or a cycloalkene mixture, b) adding a ruthenium compound of the general formula RuX1X2L1aL2b (I) where a=0 or 1, b=1 or 2, such that a+b=2; X1, X2=independently selected anionic ligands; L1=uncharged ?-binding ligand; L2=N-heterocyclic carbene of the formula IIa, IIb or IIc; c) adding a chain transfer agent in a molar ratio in the range from 1:5 to 1:1000 based on the cycloalkene or the sum total of the cycloalkenes in the cycloalkene mixture, d) converting at a temperature within a range from 0° C. to 250° C.