Isomerization of Aldehydes Catalyzed by Rhodium(I) Olefin Complexes

A mixture of isomeric aldehydes is formed in a catalytic isomerization of alkyl aldehydes with [C₅Me₅Rh(olefin)₂] complexes. This process offers an indirect method for altering the n:iso ratio of aldehydes formed in hydroformylation reactions. For example the reaction of n-butanal with [C₅Me₅Rh(CH₂=CHMe)₂] (1) results in the formation of a bis-alkyl carbonyl rhodium complex 2 which is the resting state during the isomerization of n-butanal to a mixture of n- and iso-butanals (see scheme). In the presence of other olefins transfer formylation is observed.