Hydrogenation of nitrile rubber

1. A process for preparing partially or fully hydrogenated nitrile rubbers, the process comprising subjecting a nitrile rubber to hydrogenation in the presence of at least one complex catalyst having the general formula (I)

Ru(CO)(H)(X 1 )(L 1 )(L 2 )  (I)

wherein

X 1 is an anionic ligand, and

either:

(i) L represents a N-heterocyclic carbene ligand, and

L 1 represents a phosphine having the general formula (IIf)

wherein

R 1 , R 2 and R 3 are identical or different, and represent C 1 -C 20 alkyl, C 3 -C 8 -cycloalkyl, C 1 -C 20 alkoxy, C 6 -C 20 aryloxy, C 2 -C 20 heteroaryl with at least one heteroatom in the cycle, a C 2 -C 20 heterocyclyl group with at least one heteroatom in the cycle, or halogen; or

(ii) both ligands L 1 and L 2 represent an identical or different N-heterocyclic carbene ligand.

2. The process according to claim 1 , wherein the N-heterocyclic carbene ligand is a cyclic carbene ligand with at least one nitrogen as hetero atom being present in the ring, and wherein such N-heterocyclic carbene ligand can be unsubstituted or substituted with one or more substituents.

3. The process according to claim 2 , wherein the N-heterocyclic carbene ligand has a structure corresponding to the general formulae (IIa) to (IIe)

wherein

R 8 , R 9 , R 10 and R 11 are identical or different and represent hydrogen, straight-chain or branched C 1 -C 30 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 2 -C 20 -alkynyl, C 6 -C 24 -aryl, C 7 -C 25 -alkaryl, C 2 -C 20 heteroaryl, C 2 -C 20 heterocyclyl, C 1 -C 20 -alkoxy, C 2 -C 21 -alkenyloxy, C 2 -C 20 -alkynyoxy, C 6 -C 20 -aryloxy, C 2 -C 20 -alkoxycarbonyl, C 1 -C 20 -alkylthio, C 6 -C 20 -arylthio, —Si(R) 3 , —O—Si(R) 3 , —O—C(═O)R, C(═O)R, —C(═O)N(R), —NR—C(═O)—N(R) 2 , —SO 2 N(R) 2 , —S(═)R, —S(═O) 2 R, —O—S(═O) 2 R, halogen, nitro or cyano; wherein in all above occurrences relating to the meanings of R 8 , R 9 , R 10 and R 11 the group R is identical or different and represents hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, aryl or heteroaryl and wherein one or more of R 8 , R 9 , R 10 and R 11 can independently of one another, be substituted by one or more substituents, and a functional group selected from the group consisting of hydroxy, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulphide, carbonate, isocyanate, carbodimide, carboalkoxy, carbamate and halogen, where these abovementioned substituents, to the extent chemically possible, may in turn be substituted by one or more substituents selected from the group consisting of halogen, C 1 -C 5 -alkyl, C 1 -C 5 -alkoxy and phenyl.

4. The process according to claim 3 , wherein the N-heterocyclic carbene ligand has a structure corresponding to the general formulae (IIa) to (IIe) wherein

R 8 and R 9 are identical or different and represent hydrogen, C 6 -C 24 -aryl, straight-chain or branched C 1 -C 10 -alkyl, or form a cycloalkyl or aryl structure together with the carbon atoms to which they are bound, and

R 10 and R 11 are identical or different and represent straight-chain or branched C 1 -C 10 -alkyl, C 3 -C 10 -cycloalkyl, substituted or unsubstituted C 6 -C 24 -aryl.

5. The process according to claim 3 , wherein the N-heterocyclic carbene ligand has a structure corresponding to formulae (IIIa) to (IIIu), where “Ph” means in each case phenyl, “Bu” means either n-butyl, sec.-butyl, iso-butyl or tert.-butyl, “Mes” represents in each case 2,4,6-trimethylphenyl, “Dipp” means in all cases 2,6-diisopropylphenyl and “Dimp” means 2,6-dimethylphenyl

6. The process according to claim 1 , wherein X 1 represents hydrogen, halogen, pseudohalogen, straight-chain or branched C 1 -C 30 -alkyl, C 6 -C 24 -aryl, C 1 -C 20 -alkoxy, C 6 -C 24 -aryloxy, C 3 -C 20 -alkyldiketonate, C 6 -C 24 -aryldiketonate, C 1 -C 20 -carboxylate, C 1 -C 20 -alkylsulfonate, C 6 -C 24 -arylsulfonate, C 1 -C 20 -alkythiol, C 6 -C 24 -arylthiol, C 1 -C 20 -alkylsulfonyl or C 1 -C 20 -alkysulfinyl, and wherein all aforementioned moieties can be unsubstituted or also be substituted by one or more further substituents, selected from the group consisting of halogen, C 1 -C 10 -alkyl, C 1 -C 10 -alkoxy or C 6 -C 24 -aryl, and where these substituents may in turn also be substituted by one or more substituents selected from the group consisting of halogen, C 1 -C 5 -alkyl, C 1 -C 5 -alkoxy and phenyl.

7. The process according to claim 1 , wherein X 1 represents chlorine, CF 3 COO, CH 3 COO, CFH 2 COO, (CH 3 ) 3 CO, (CF 3 ) 2 (CH 3 )CO, (CF 3 )(CH 3 ) 2 CO, phenoxy, methoxy, ethoxy, p-CH 3 —C 6 H 4 —SO 3 , CH 3 SO 3 or CF 3 SO 3 .

8. The process according to claim 1 , wherein a catalyst of formulae (I-c) is used

wherein L 2 represents a ligand of the general formulae (IIa) or (IIb)

wherein

R 8 and R 9 are identical or different and represent hydrogen, C 6 -C 24 -aryl, straight-chain or branched C 1 -C 10 -alkyl, or form a cycloalkyl or aryl structure together with the carbon atoms to which they are bound, and

R 10 and R 11 are identical or different and represent straight-chain or branched C 1 -C 10 -alkyl, C 3 -C 10 -cycloalkyl, substituted or unsubstituted C 1 -C 24 -aryl, C 1 -C 10 -alkylsulfonate, or C 5 -C 10 -arylsulfonate,

or wherein L 2 represents a ligand of the general formulae (IIIa) to (IIIu) where “Ph” means in each case phenyl, “Bu” means in each case butyl, “Mes” represents in each case 2,4,6-trimethylphenyl, “Dipp” means in all cases 2,6-diisopropylphenyl and “Dimp” means in each case 2,6-dimethylphenyl

9. The process according to claim 1 , wherein the hydrogenation is carried out at a temperature of 60° C. to 200° C., and at a hydrogen pressure of 0.5 MPa to 35 MPa.

10. The process according to claim 1 , wherein the amount of the complex catalyst to the nitrile rubber is 1 to 1000 ppm of noble metal, based on the nitrile rubber used.

11. The process according to claim 1 , wherein the nitrile rubber subjected to hydrogenation is a copolymer or terpolymer comprising repeating units of

(i) at least one α, β-unsaturated nitrile,

(ii) at least one conjugated diene, and

(iii) optionally one or more further copolymerizable monomers selected from the group consisting of α,β-unsaturated monocarboxylic acids, their esters and amides, α,β-unsaturated dicarboxylic acids, their mono- or diesters and the respective anhydrides or amides of said α,β-unsaturated dicarboxylic acids.

12. The process according to claim 1 , wherein L 1 is selected from the group consisting of P(CF 3 ) 3 , P(CH 2 C 6 H 4 —SO 3 Na) 3 , P(isopropyl) 3 , P(CHCH 3 (CH 3 CH 3 )) 3 , P(cyclopentyl) 3 , P(cyclohexyl) 3 , and P(neopentyl).

13. The process according to claim 12 , wherein:

the nitrile rubber comprises repeating units of at least one α, β-unsaturated nitrile, and at least one conjugated diene;

the hydrogenation is carried out at a temperature of 60° C. to 200° C., at a hydrogen pressure of 0.5 MPa to 35 MPa;

X 1 represents chlorine, CF 3 COO, CS 3 COO, CFH 2 COO, (CH 3 ) 3 CO, (CF 3 ) 2 (CH)CO, (CF 3 )(CH 3 ) 2 CO, phenoxy, methoxy, ethoxy, p-CH 3 —C 6 H 4 —SO 3 , CH 3 SO 3 or CF 3 SO 3 ; and

L 2 is an N-heterocyclic carbene ligand having a structure corresponding to formulae (IIIa) to (IIIu), where “Ph” means in each case phenyl, “Bu” means either n-butyl, sec.-butyl, iso-butyl or tert.-butyl, “Mes” represents in each case 2,4,6-trimethylphenyl, “Dipp” means in all cases 2,6-diisopropylphenyl and “Dimp” means 2,6-dimethylphenyl

14. The process according to claim 1 , wherein the catalyst is a catalyst according to formulae (I-c(1)) or (I-d(1))