A process for preparation of ruthenium-based carbene catalysts with chelating alkylidene ligands by reacting a ruthenium-alkylidene complex with an olefin derivate in a cross metathesis reaction in the presence of a polymer-supported cation exchange resin according to equation: wherein - L 1 is a neutral 2-electron donor ligand, - L 2 is a neutral amine or phosphine ligand, - X 1 and X 2 are, independently from each other, inorganic or organic anionic ligands, such as halide anions, pseudohalide anions, hydroxides, acetates, trifluoracetates or carboxylates, - Y 1 and Y 2 are, independently form each other, hydrogen, C 1 -C 6 -alkyl, C 2 -C 6 -alkenyl, C 2 -C 6 -alkynyl, C 1 -C 6 -alkylthio, phenyl, aryl, arylthio, C 1 -C 6 -alkylsulfonyl or C 1 -C 6 -alkylsulfinyl, or Y 1 and Y 2 are taken together to form a ring of the indenylidene type according to the formula wherein in said formula R 3 is hydrogen or a substituted or unsubstituted phenyl group, - R 0 and R 1 are, independently from each other, hydrogen, C 1 -C 10 -alkyl, C 2 -C 10 -alkenyl, C 2 -C 10 -alkynyl, a phenyl or an aryl group (which optionally can be substituted), - a, b, c and d are, independent from each other, hydrogen, C 1 -C 10 -alkyl, C 1 -C 10 -alkoxy, C 1 -C 10 -alkylthio, C 1 -C 10 -silanyl, C 1 -C 10 -silyloxy, C 2 -C 10 -alkenyl, C 2 -C 10 -alkynyl, C 6 -C 14 -aryl, C 6 -C 14 -aryloxy, C 6 -C 14 -heterocyclic, C 6 -C 14 -heterocyclic aryl, phenyl, fluoro (-F), chloro (-Cl), bromo (-Br), iodo (-I), trifluormethyl (-CF 3), nitro (-NO 2), sulfinyl, sulfonyl, formyl, C 1 -C 10 -carbonyl, C 1 -C 10 -ester, C 1 -C 10 -aminocarbonyl, C 1 -C 10 -alkylamido, C 1 -C 10 -sulfonamido, C 1 -C 10 -uramido, C 1 -C 10 -aminosulfonyl, and ionic groups such as -[C 5 H 6] + PF 6 - or - [N(C 2 H 5) 2 CH 3] + Cl -, with the provision that each of a, b, c or d can form a ring with each other, - Z is a heterodonor atom such as oxygen or sulphur or a group comprising a heterodonor atom such as sulfinyl (>S=O), - R 2 is a substituted or unsubstituted hydrocarbon group, such as alkyl, alkenyl, alkynyl, aryl, alkylamino, alkylthio, a substituted or unsubstituted keto group such as -C(R a) 2 -CO-C(R b) 3, a substituted or unsubstituted ester group such as -C(R a) 2 -CO-O(R c) (wherein in said groups R a is hydrogen or C 1 -C 10 -alkyl, R b is hydrogen, C 1 -C 10 -alkyl, C 1 -C 10 -fluoroalkyl, C 1 -C 10 -alkylamino, C 1 -C 10 -alkyl ammonium or C 2 -C 10 -alkenyl and R c is C 1 -C 10 -alkyl, C 1 -C 10 -fluoroalkyl, C 1 -C 10 -alkylamino, C 1 -C 10 -alkyl ammonium or C 2 -C 10 -alkenyl) with the provision that R 2 and/or Z may form a ring with d, - PSR is a polymer-supported cation-exchange resin and - PSR-L 2 is the adduct of the polymer-supported cation-exchange resin with ligand L2, and wherein the polymer-supported cation-exchange resin comprises acidic groups or acid chloride groups and is added in quantities in the range of 2 to 10 equivalents based on the starting Ru alkylidene complex. - L 1 is a neutral 2-electron donor ligand, - L 2 is a neutral amine or phosphine ligand, - X 1 and X 2 are, independently from each other, inorganic or organic anionic ligands, such as halide anions, pseudohalide anions, hydroxides, acetates, trifluoracetates or carboxylates, - Y 1 and Y 2 are, independently form each other, hydrogen, C 1 -C 6 -alkyl, C 2 -C 6 -alkenyl, C 2 -C 6 -alkynyl, C 1 -C 6 -alkylthio, phenyl, aryl, arylthio, C 1 -C 6 -alkylsulfonyl or C 1 -C 6 -alkylsulfinyl, or Y 1 and Y 2 are taken together to form a ring of the indenylidene type according to the formula wherein in said formula R 3 is hydrogen or a substituted or unsubstituted phenyl group, - R 0 and R 1 are, independently from each other, hydrogen, C 1 -C 10 -alkyl, C 2 -C 10 -alkenyl, C 2 -C 10 -alkynyl, a phenyl or an aryl group (which optionally can be substituted), - a, b, c and d are, independent from each other, hydrogen, C 1 -C 10 -alkyl, C 1 -C 10 -alkoxy, C 1 -C 10 -alkylthio, C 1 -C 10 -silanyl, C 1 -C 10 -silyloxy, C 2 -C 10 -alkenyl, C 2 -C 10 -alkynyl, C 6 -C 14 -aryl, C 6 -C 14 -aryloxy, C 6 -C 14 -heterocyclic, C 6 -C 14 -heterocyclic aryl, phenyl, fluoro (-F), chloro (-Cl), bromo (-Br), iodo (-I), trifluormethyl (-CF 3), nitro (-NO 2), sulfinyl, sulfonyl, formyl, C 1 -C 10 -carbonyl, C 1 -C 10 -ester, C 1 -C 10 -aminocarbonyl, C 1 -C 10 -alkylamido, C 1 -C 10 -sulfonamido, C 1 -C 10 -uramido, C 1 -C 10 -aminosulfonyl, and ionic groups such as -[C 5 H 6] + PF 6 - or - [N(C 2 H 5) 2 CH 3] + Cl -, with the provision that each of a, b, c or d can form a ring with each other, - Z is a heterodonor atom such as oxygen or sulphur or a group comprising a heterodonor atom such as sulfinyl (>S=O), - R 2 is a substituted or unsubstituted hydrocarbon group, such as alkyl, alkenyl, alkynyl, aryl, alkylamino, alkylthio, a substituted or unsubstituted keto group such as -C(R a) 2 -CO-C(R b) 3, a substituted or unsubstituted ester group such as -C(R a) 2 -CO-O(R c) (wherein in said groups R a is hydrogen or C 1 -C 10 -alkyl, R b is hydrogen, C 1 -C 10 -alkyl, C 1 -C 10 -fluoroalkyl, C 1 -C 10 -alkylamino, C 1 -C 10 -alkyl ammonium or C 2 -C 10 -alkenyl and R c is C 1 -C 10 -alkyl, C 1 -C 10 -fluoroalkyl, C 1 -C 10 -alkylamino, C 1 -C 10 -alkyl ammonium or C 2 -C 10 -alkenyl) with the provision that R 2 and/or Z may form a ring with d, - PSR is a polymer-supported cation-exchange resin and - PSR-L 2 is the adduct of the polymer-supported cation-exchange resin with ligand L2, and wherein the polymer-supported cation-exchange resin comprises acidic groups or acid chloride groups and is added in quantities in the range of 2 to 10 equivalents based on the starting Ru alkylidene complex.