Use of a catalyst of the general formula (I) wherein X and X 1 in each case independently of one another are halogens, preferably selected from the group consisting of Cl, Br and I, L is an uncharged ligand of the formula L 1 , L 2 , L 3 or L 4 , wherein R 10 and R 11 in each case independently of one another are a substituted or unsubstituted side chain comprising 1 to 30 carbon atoms and optionally comprising one or more functional groups, and wherein R 12 and R 13 in each case independently of one another are H, C 1-6 alkyl, optionally substituted with an alkoxy radical OR 15 , or aryl optionally substituted with an alkoxy radical OR 15 , or form a 3- or 4-membered alkene bridge, and wherein R 15 is selected from the group consisting of C 1-20 alkyl, aryl and C 7-18 aralkyl, and wherein g and g' are in each case halogens, z is a methyl or carbonyl group, a, b and c are in each case H; R 2 is selected from the group consisting of H, C 1-12 alkyl, preferably methyl, ethyl or isopropyl, C 5-12 cycloalkyl, C 7-18 aralkyl or aryl; and R 3 is selected from the group consisting of H, C 1-12 alkyl, C 5-12 cycloalkyl, C 7-18 aralkyl, aryl, C 1-12 haloalkyl, C 1-12 ammonium alkyl, C 1-12 pyridinium alkyl, C 1-12 aldehyde alkyl, C 1-12 nitroalkyl, nitrile or a radical selected from the group consisting of ketones COR 4 , esters CO 2 R 4 , oxalates COCO 2 R 4 , sulfones SO 2 R 4 or amides CONHR 4 , where R 4 is selected from the group consisting of H, C 1-12 alkyl, C 5-12 cycloalkyl, C 7-18 aralkyl, aryl, C 1-12 haloalkyl, C 1-12 ammonium alkyl, C 1-12 pyridinium alkyl, C 1-12 aldehyde alkyl, C 1-12 nitroalkyl and nitrile, or R 3 is a side chain of the formula R 3c , R 3d , R 3e , R 3f , R 3g , R 3h , R 3i , R 3j , R 3k , R 3l , R 3m , R 3n , R 3o or R 3p : or, if z is methyl, R 3 is a side chain of the formula R 3a or R 3b : wherein A - is selected from the group consisting of F - , Cl - , Br, I - , tetrafluoroborate BF 4 - , hexafluorophosphate PF 6 - and bis(trifluoromethylsulfonyl)amide NTf 2 - , in a method for the metathesis of nitrile rubber. X and X 1 in each case independently of one another are halogens, preferably selected from the group consisting of Cl, Br and I, L is an uncharged ligand of the formula L 1 , L 2 , L 3 or L 4 , wherein R 10 and R 11 in each case independently of one another are a substituted or unsubstituted side chain comprising 1 to 30 carbon atoms and optionally comprising one or more functional groups, and wherein R 12 and R 13 in each case independently of one another are H, C 1-6 alkyl, optionally substituted with an alkoxy radical OR 15 , or aryl optionally substituted with an alkoxy radical OR 15 , or form a 3- or 4-membered alkene bridge, and wherein R 15 is selected from the group consisting of C 1-20 alkyl, aryl and C 7-18 aralkyl, and wherein g and g' are in each case halogens, z is a methyl or carbonyl group, a, b and c are in each case H; R 2 is selected from the group consisting of H, C 1-12 alkyl, preferably methyl, ethyl or isopropyl, C 5-12 cycloalkyl, C 7-18 aralkyl or aryl; and R 3 is selected from the group consisting of H, C 1-12 alkyl, C 5-12 cycloalkyl, C 7-18 aralkyl, aryl, C 1-12 haloalkyl, C 1-12 ammonium alkyl, C 1-12 pyridinium alkyl, C 1-12 aldehyde alkyl, C 1-12 nitroalkyl, nitrile or a radical selected from the group consisting of ketones COR 4 , esters CO 2 R 4 , oxalates COCO 2 R 4 , sulfones SO 2 R 4 or amides CONHR 4 , where R 4 is selected from the group consisting of H, C 1-12 alkyl, C 5-12 cycloalkyl, C 7-18 aralkyl, aryl, C 1-12 haloalkyl, C 1-12 ammonium alkyl, C 1-12 pyridinium alkyl, C 1-12 aldehyde alkyl, C 1-12 nitroalkyl and nitrile, or R 3 is a side chain of the formula R 3c , R 3d , R 3e , R 3f , R 3g , R 3h , R 3i , R 3j , R 3k , R 3l , R 3m , R 3n , R 3o or R 3p : <EOS>