A comparative study has been made of transition metal-catalyzed hydroformylation of hex-1-ene using rhodium, cobalt and ruthenium complexes of triphenylphosphine, triphenylarsine and triphenylantimony as catalysts. The catalytic activities of the ligands with the studied metals vary in the order: Ph3P approximate to Ph3As > Ph3Sb under employed reaction conditions. The hydroformylation activity of M/AsPh3. Systems was comparable and even higher under some experimental conditions than that of M/PPh3 systems. The only significant difference, which makes M/PPh3 systems better than M/AsPh3 systems, was the higher normal/iso (n/iso) ratio of heptanal for M/PPh3 Systems. (c) 2004 Elsevier B.V. All rights reserved.