Platinum complexes having 1,2-substituted benzyl-based diphosphine ligands for the catalysis of the alkoxycarbonylation of ethylenically unsaturated compounds

Complex comprising Pt and a compound of formula (I)

• where
• R1, R2, R3, R4 are each independently selected from —(C1-C12)-alkyl, —(C3-C12)-cycloalkyl, —(C3-C12)-heterocycloalkyl, —(C6-C20)-aryl, —(C6-C20)-heteroaryl;
• at least one of the R1, R2, R3, R4 radicals is a —(C6-C20)-heteroaryl radical having at least six ring atoms;
• and
• R1, R2, R3, R4, if they are —(C1-C12)-alkyl, —(C3-C12)-cycloalkyl, —(C3-C12)-heterocycloalkyl, —(C6-C20)-aryl or —(C6-C20)-heteroaryl,
• may each independently be substituted by one or more substituents selected from:
• —(C1-C12)-alkyl, —O—(C1-C12)-alkyl, —OH, —NH2, halogen.