Use of catalysts for the metathesis of nitrile rubber

A method comprising the use of at least one catalyst of the general formula (I)

• wherein
• X and X1 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 L1, L2, L3 or L4,
• wherein R10 and R11 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 R12 and R13 in each case independently of one another are H, C1-6 alkyl, optionally substituted with an alkoxy radical OR15, or aryl optionally substituted with an alkoxy radical OR15, or form a 3- or 4-membered alkene bridge, and
• wherein R15 is selected from the group consisting of C1-20 alkyl, aryl and C7-18 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;
• R2 is selected from the group consisting of H, C1-12 alkyl, preferably methyl, ethyl or isopropyl, C5-12 cycloalkyl, C7-18 aralkyl or aryl;
• and
• R3 is selected from the group consisting of H, C1-12 alkyl, C5-12 cycloalkyl, C7-18 aralkyl, aryl, C1-12 haloalkyl, C1-12 ammonium alkyl, C1-12 pyridinium alkyl, C1-12 aldehyde alkyl, C1-12 nitroalkyl, nitrile or a radical selected from the group consisting of ketones COR4, esters CO2R4, oxalates COCO2R4, sulfones SO2R4 or amides CONHR4, where R4 is selected from the group consisting of H, C1-12 alkyl, C5-12 cycloalkyl, C7-18 aralkyl, aryl, C1-12 haloalkyl, C1-12 ammonium alkyl, C1-12 pyridinium alkyl, C1-12 aldehyde alkyl, C1-12 nitroalkyl and nitrile, or R3 is a side chain of the formula R3c, R3d, R3e, R3f, R3g, R3h, R3i, R3j, R3k, R3l, R3m, R3n, R3o, or R3p:
• or, if z is methyl, R3 is a side chain of the formula R3a or R3b:
• wherein A− is selected from the group consisting of F−, Cl−, Br−, I−, tetrafluoroborate BF4−, hexafluorophosphate PF6− and bis(trifluoromethylsulfonyl)amide NTf2−,
• which the at least one catalyst is used in the metathesis reaction of nitrile rubber.