Abstract: Cationic rhodium bis(dioxaphosphorus heterocycle) complexes of the formula: ##STR1## in which R is preferably ##STR2## or (CH.sub.2).sub.2-5, Y . . . Y is any backbone chain of 2-5 atoms, and L and L' are any stabilizing ligands, used in hydroformylation of olefins to obtain regioselectivity of branched aldehyde products. The formula of the catalyst may include substituents which do not interfere with the branched product regioselectivity of the catalyst as a whole. In the hydroformylation method the olefin is reacted with hydrogen and carbon monoxide in the presence of the catalyst at a temperature and pressure sufficient to permit the desired branched product regioselectivity.

Abstract: Cationic rhodium bis(dioxaphosphorus heterocycle) complexes of the formula: ##STR1## in which R is preferably ##STR2## or (CH.sub.2).sub.2-5, Y . . . Y is any backbone chain of 2-5 atoms, and L and L' are any stabilizing ligands, used in hydroformylation of olefins to obtain regioselectivity of branched aldehyde products. The formula of the catalyst may include substituents which do not interfere with the branched product regioselectivity of the catalyst as a whole. In the hydroformylation method the olefin is reacted with hydrogen and carbon monoxide in the presence of the catalyst at a temperature and pressure sufficient to permit the desired branched product regioselectivity.