Hydroformylation of olefins

In a hydroformylation process, wherein a C.sub.2-20 monounsaturated alpha-olefin, carbon monoxide, and hydrogen are reacted in the presence of a catalyst comprising a complex of a phosphine ligand and rhodium to produce normal straight chain and iso saturated aldehyde isomers, at a pressure from 100-1,000 psi, the improvement for producing a high normal/iso isomer ratio and without forming sparingly soluble catalyst complexes, which comprises effecting said reaction in the presence of a catalyst comprising a complex of a rhodium compound and chelating phosphine ligand, the chelating phosphine ligand being represented by the formula:

• R.sub.1 R.sub.2 P A P R.sub.3 R.sub.4 wherein:
• R.sub.1 and R.sub.3 are alkenyl groups having from 2 to 6 carbon atoms, alkyl groups having from 1 to 6 carbon atoms, hydrogen atoms, phenyl groups, and substituted derivatives thereof;
• R.sub.2 and R.sub.4 are phenyl groups and substituted phenyl groups;
• A is an alkenyl group having from 2 to 4 carbon atoms;
• and (CH.sub.2).sub.n wherein n is from 2 to 10 and substituted derivatives thereof;
• and
• the molar ratio of said ligand to rhodium is from about 0.6-1.2:1 provided that where A is (CH.sub.2).sub.n and n is from 5-10, then the molar ratio is from 1-5:1.