Abstract: An organo metallic complex catalyst, useful in the hydroformylation of an olefin, e.g., an alkene, to yield an aldehyde product in which the normal aldehyde isomer predominates over branch-chain isomers, which has the structure: ##STR1## wherein capital M is a Group VIII metal (preferably rhodium); Q is phosphorus, arsenic, or antimony (preferably phosphorus); and R is phenyl or a lower alkyl group.In the process employing the new catalytic complex it is not necessary to employ an excess of any ligand, and moderate reaction conditions are adequate. The catalyst can be prepared ex situ or in situ from a suitable source of rhodium or the Group VIII metal and a suitable derivative of ferrocene.