The title complex (I) was prepared from [Rh(CO)2Cl]2 and the sodium salt of salicylaldoximine. In the presence of phosphines I was an active catalyst precursor for the hydroformylation of styrene at 60?0.1 MPa. The activity and selectivity increased as the phosphine ligands were changed from mono- to diphosphines. In the presence of 1,3-bis(diphenylphosphino)propane, an optimum catalyst activity of 1.6 min-1 was achieved, and the regioselectivity to 2-phenylpropanal was up to 90%. The sequence of phosphines for the regioselectivity to 2-phenylpropanal is in good accord with their s-electron donating abilities, i.e., Ph2P(CH2)3PPh2 u Ph2P(CH2)2PPh2 > PPh3 > P(OPh)3. An increase in the P/Rh ratio, except for PPh3 as ligand, led to a decrease in catalyst activity, but a small excess of phosphines favored the stability of the catalyst and the P/Rh ratio did not affect the regioselectivity remarkably. No side reactions such as hydrogenation were found; the chemoselectivity to aldehyde is 100%.

Key words: CATALYST, HYDROGENATION, STYRENE, PHOSPHINE, RHODIUM COMPLEX, FORMYLATION, CATALYTIC ACTIVITY, SALICYL ALDOXIME P, PHOSPHORUS ACID ESTERS