Process for the preparation of low molecular weight hydrogenated nitrile rubber

A process for the preparation of a hydrogenated nitrile rubber comprising the steps of

• a) reacting a nitrile rubber in the presence of at least one co-olefin and at least one compound selected from the group consisting of compounds of the general formulas I, II, III or IV,
• wherein
• M is Os or Ru,
• R and R1 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 alkyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl,
• X and X1 are independently any anionic ligand,
• L and L1 are, independently any neutral ligand, optionally, L and L1 can be linked to one another to from a bidentate neutral ligand;
• wherein
• M1 is Os or Ru;
• R2 and R3 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 alkyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl,
• X2 is a anionic ligand, and
• L2 is a neutral mono- or polycyclic □-bonded ligand,
• L3 is a ligand selected from the group consisting of phosphines, sulfonated phosphines, fluorinated phosphines, functionalized phosphines bearing up to three aminoalkyl-, ammoniumalkyl-, alkoxyalkyl-, alkoxylcarbonylalkyl-, hydrocycarbonylalkyl-, hydroxyalkyl- or ketoalkyl- groups, phosphites, phosphinites, phosphonites, phosphinamines, arsines, stibenes, ethers, amines, amides, imines, sulfoxides, thioethers and pyridines,
• Y− is a non-coordinating anion,
• n is an integer in the range of from 0 to 5,
• wherein
• M2 is Mo or W,
• R4, R5 are, independently, hydrogen or a hydrocarbon selected from the group consisting of C2-C20 alkenyl, C2-C20 alkynyl, C1-C20 alkyl, aryl, C1-C20 carboxylate, C1-C20 alkoxy, C2-C20 alkenyloxy, C2-C20 alkynyloxy, aryloxy, C2-C20 alkoxycarbonyl, C1-C20 alkylthio, C1-C20 alkylsulfonyl and C1-C20 alkylsulfinyl;
• R6 and R7 are independently any unsubstituted or halo-substituted alkyl, aryl, aralkyl groups or silicon-containing analogs thereof,
• wherein
• M is Os or Ru,
• R and R1 are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, and substituted or unsubstituted alkyl
• X and X1 are independently any anionic ligand, and
• L an L1 are independently any neutral ligand;
• and
• b) hydrogenating the product of step a).