alpha-Dicationic Chelating Phosphines: Synthesis and Application to the Hydroarylation of Dienes

A series Of new P boolean AND P-chelating ligands constituted by a dicationic [P(H(2)Im)(2)](+2) unit (H(2)Im = 1,3-clitnethy1-4,5-dihydroimidazol-2-ylidene) and a PPh2 group connected through structurally different backbones have been synthesized. Evaluation -of their reactivity toward different metal centers provides evidence that the dicationic fragment, otherwise reluctant to coordinate metals, readily participates in the formation of chelates when embedded into such a scaffold, Moreover, it significantly enhances the Lewis acidity of the metals to which it coordinates. This property has been used to develop a Rh catalyst that efficiently triggers the hydroarylation of dienes with electron -rich aromatic molecules. Kinetic studies and deuterium -labeling experiments, as well as density functional theory calculations,. were performed in order to rationalize these findings.