Electronic Ligand Effects on the Regioselectivity of the Rhodium−Diphosphine-Catalyzed Hydroformylation of Propene

Abstract

Electronic effects induced by diphosphine bidentate ligands on the regioselectivity of the rhodium-catalyzed hydroformylation of propene were investigated using density functional theory based calculations (B3LYP). To this end, the key hydride migration step was evaluated for HRh(propene)(CO)L2 (L2 = PF3, PF3; PH3, PH3; PMe3, PMe3; PH3, PF3; PH3, PMe3) incorporating either two identical or two electronically distinct phosphorus moieties. The phosphorus moieties span a wide range of ligand basicities. While the electronic properties of the ligands do not influence the regioselectivity of the hydride migration reaction directly, they do govern the amount of back-donation from the metal to the alkene substrate. As a result, important differences in transition-state geometries are obtained for different ligand systems. For electron-withdrawing ligands low activation energies and trigonal-bipyramidal transition-state geometries are observed. Increasing the basicity of the diphosphine ligand leads to higher act...