On the origin of diastereofacial selectivity in the interaction of β-pinene with rhodium carbonyl: A density functional study

In this work we have performed electronic structure calculations at the density functional theory (DFT) level in order to understand the structural, electronic and energetic factors involved in the diastereofacial selectivity in the interaction of β-pinene with [HRh(CO)3], used as a model for the unmodified rhodium catalyst of hydroformylation. Analysis of the nature of the metal-ligand interaction of the π-complexes revealed that the catalyst coordination through the more sterically hindered face of β-pinene generates a stronger π-complex, however, being thermodynamically less stable due to the smaller steric hindrance for the catalyst coordination on the other face of the olefin. Our energetic results show that despite the coordination of the olefin to the more sterically hindered face being thermodynamically less favorable, the lower activation energy (8.5 kcal mol−1), the higher stability of the metal-alkyl product (−10.1 kcal mol−1) and the absence of an isomerization pathway for this coordination mode, are responsible for the dramatic preference for this pathway, observed experimentally.