ChemInform Abstract: Electron Withdrawing Substituents on Equatorial and Apical Phosphines Have Opposite Effects on the Regioselectivity of Rhodium‐Catalyzed Hydroformylation.

Abstract

Electron Withdrawing Substituents on Equatorial and Apical Phosphines Have Opposite Effects on the Regioselectivity of Rhodium-Catalyzed Hydroformylation.-Chelating diphosphines designed to coordinate in diequatorial or in apical-equatorial positions are synthesized. From Ir-complexes as models for catalytic species it is shown that only diequatorial coordination is observed for (I) complexes and only apical-equatorial coordination for (III) complexes. For (II) complexes, a mixture of diequatorial and apical-equatorial complexes is seen. In the Rh-catalyzed hydroformylation of 1-hexene minor changes in the electronic character of phosphine ligands afford significant changes in aldehyde regioselectivity. In contrast to the aryl-unsubstituted ligands hydroformylation results show with the electron withdrawing diequatorial coordinated ligand (I) an increase in linear aldehyde selectivity as well as rate, while the apical-equatorial coordinated ligand (III) shows a decrease in linear aldehyde selectivity. -(CASEY, C. P.; PAULSEN, E. L.; BEUTTENMUELLER, E. W.; PROFT, B. R.; PETROVICH, L. M.; MATTER, B. A.; POWELL, D. R.; J.

Enhancing catalytic performance of activated carbon supported Rh catalyst on heterogeneous hydroformylation of 1-hexene via introducing surface oxygen-containing groups

“…In homogeneous catalysis, the catalyst selectivity can be adjusted by some electron withdrawing aryl substituents, or functional groups such as carboxylic acid, ester or ketone groups). [21][22][23][24][25] For instance, Wakamatsu et al found that the shift of carbon double bond was strongly influenced by the functional groups in functionalized internal alkenes. [22] Casey et al investigated the different effects of aryl substituents linked at equatorial and apical diphosphines ligand on the selectivity of n-aldehyde.…”

“…[22] Casey et al investigated the different effects of aryl substituents linked at equatorial and apical diphosphines ligand on the selectivity of n-aldehyde. [25] In heterogeneous catalyst, the surface properties of catalysts are also very important, such as the surface functional groups, heteroatom doping and hydrophobicity-hydrophilicity balance, which can affect the catalytic activity and product selectivity. [26,27] However, to our knowledge, the influence of the surface properties on the catalytic performance of heterogeneous hydroformylation is rarely reported.…”