Olefin insertion into the rhodium-hydrogen bond as the step determining the regioselectivity of rhodium-catalyzed hydroformylation of vinyl substrates: Comparison between theoretical and experimental results

A comparison between experimental and theoretical data on regioselectivity concerning the hydroformylation of several vinyl substrates (propene, 2-met hylpropene, 1-hexene, 3,3-dimethylbutene, fluoroethene, 3,3,3-trifluoroprop ene, vinylmethylether, allylmethylether, styrene) with unmodified rhodium c atalysts is reported. Various H-Rh(CO)(3)-olefin complexes are examined at the B3P86/3-21G or /6-31G* level (LANL2DZ for Rh) and compared to the adduc ts with modified catalysts, such as H-RhPH3(CO)(2). The computed geometries are in satisfactory agreement with the X-ray ones. The activation energies for the alkyl rhodium intermediate formation, computed at either level alo ng the pathways to branched or linear aldehydes, allow one to predict the r egioselectivity ratios, since they are in very good agreement with the expe rimental ones evaluated for the isomeric aldehydes.