Low pressure rhodium catalyzed hydroformylation of olefins

The catalyst comprising rhodium complexed with:

• (a) a ligand of the formula ##STR13## wherein Ar is selected from aromatic ring compounds having 6 up to 14 carbon atoms;
• the x bonds and the y bonds are attached to adjacent carbon atoms on the ring structure;
• each R, when present as a substituent, is independently selected from alkyl, alkoxy, aryloxy, aryl, aralkyl, alkaryl, alkoxyalkyl, cycloaliphatic, halogen (except Cl, Br or I on the aromatic nucleus on the carbon atom adjacent to the carbon atoms bearing the x and/or y bonds), alkanoyl, alkanoyloxy, alkoxycarbonyl, formyl, carboxylate moieties, sulfonic acid derivatives, or amino moieties;
• n is a whole number in the range of 0-4 wherein Ar is phenyl;
• 0-6 wherein Ar is naphthyl;
• and 0-8 where Ar is phenanthryl or anthracenyl;
• each R.sub.1 and R.sub.2 is independently selected from alkyl, aryl, aralkyl, alkaryl, cycloaliphatic radicals and substituted derivatives thereof;
• each R.sub.3 and R.sub.4 is independently selected from hydrogen and the R.sub.1 substituents;
• each of the above alkyl groups or moieties is straight or branched chain of 1-20 carbons, preferably 1-8 carbons;
• each aryl group contains 6-10 ring carbons;
• each cycloaliphatic group contains from 4-8 ring carbons;
• and
• each Y is independently selected from elements P, As, Sb and Bi;
• in a molar ratio of ligand/Rh of about 1/1;
• (b) H in an atomic ratio of H/Rh of about 1/1;
• and
• (c) carbon monoxide in a molar ratio of CO/Rh of about 2/1.