Phosphorous acid P,P′-[5,5′,6,6′-tetramethyl-3,3′-bis(l- methylethyl)[1,1′-biphenyl]-2,2′-diyl] P,P,P′,P'-tetrakis(2,4-dimethylphenyl) ester in hydroformylation

1. A symmetric bidentate metal ligand complex mixture comprising a compound represented by formula (2):

and a metal atom selected from the group consisting of Rh, Ru, Co and Ir, wherein the symmetric bidentate metal ligand complex mixture has a chlorine value according to Wickhold below 10,000 ppm.

2. The bidentate metal ligand complex mixture according to claim 1 , wherein M is Rh.

3. A process for converting an olefin to an aldehyde comprising the process steps of:

a1) initially charging an olefin having 2 to 24 carbon atoms,

b1) adding

the symmetric bidentate metal ligand complex mixture according to claim 1 ,

c1) feeding in H 2 and CO,

d1) heating the reaction mixture, with conversion of the olefin to an aldehyde.

4. The process according to claim 3 , characterized in that the metal atom is Rh.

5. The process according to claim 3 , wherein the olefin having 2 to 24 carbon atoms is selected from ethene, propene butene, 1-butene or 2-butene.

6. The process according to claim 3 , characterized in that, in step a1), wherein the olefin having 2 to 24 carbon atoms is selected from 1-butene or 2-butene.

7. A catalytic hydroformylation process comprising contacting an olefin with

the symmetric bidentate metal ligand complex mixture according to claim 1 .

8. The process according to claim 7 , wherein the hydroformylation process converts the olefin to substituted or unsubstituted aldehydes having 3 to 20 carbon atoms, including substituted or unsubstituted propenals, butanals, pentanals, nonanals, tridecanals, substituted or unsubstituted propenals, butanals or pentanals.

9. The process according to claim 7 , wherein the substituted or unsubstituted aldehydes having 3 to 20 carbon atoms include substituted or unsubstituted propenals, butanals or pentanals.