Platinum complexes having ferrocene diphosphine ligands for catalysis of the hydroxycarbonylation of ethylenically unsaturated compounds

1. A process comprising:

a) adding an ethylenically unsaturated compound to form a reaction mixture;

b) adding to the reaction mixture a platinum complex having a ferrocene-diphosphine ligand of formula (I)

where

R 1 , R 2 , R, and R 4 are each independently selected from —(C 1 -C 12 )-alkyl, —(C 6 -C 20 )— or heteroaryl or

adding to the reaction mixture the ligand of formula (I) and a Pt compound;

c) adding to the reaction mixture an acid;

d) feeding into the reaction mixture CO;

e) heating the reaction mixture formed from a) to d), to convert the ethylenically unsaturated compound to a carboxylic acid.

2. The process according to claim 1 ,

wherein the ethylenically unsaturated compound is selected from: ethene, propene, 1-butene, cis- and/or trans-2-butene, isobutene, 1,3-butadiene, 1-pentene, cis- and/or trans-2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, hexene, tetramethylethylene, heptene, 1-octene, 2-octene, di-n-butene, or mixtures thereof.

3. The process according to claim 1 ,

wherein the acid is selected from: acetic acid, perchloric acid, sulfuric acid, phosphoric acid, methylphosphonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid, 2-hydroxypropane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, dodecylsulfonic acid or camphorsulfonic acid.

4. The process according to claim 1 ,

wherein the acid is acetic acid.

5. The process according to claim 1 ,

wherein the Pt compound is selected from: platinum dichloride (PtCl 2 ), platinum(II) acetylacetonate [Pt(acac) 2 ], platinum(II) acetate [Pt(OAc) 2 ], dichloro(1,5-cyclooctadiene)platinum(II) [Pt(cod) 2 Cl 2 ], bis(dibenzylideneacetone)platinum[Pt(dba) 2 ], bis(acetonitrile)dichloroplatinum(II) [Pt(CH 3 CN) 2 Cl 2 ] or (cinnamyl)platinum dichloride [Pt(cinnamyl)Cl 2 ].

6. The process according to claim 1 ,

wherein the Pt compound is selected from: platinum dichloride (PtCl 2 ), platinum(II) acetylacetonate [Pt(acac) 2 ] or platinum(II) acetate [Pt(OAc) 2 ].

7. The process according to claim 1 ,

wherein the R 1 and R 3 radicals are each 2-pyridyl.

8. The process according to claim 7 ,

wherein R 2 and R 3 are —(C 1 -C 12 )-alkyl.

9. The process according to claim 8 ,

wherein R 2 and R 4 are tert-butyl.