Ir-Catalyzed Asymmetric Allylic Substitutions with (Phosphoramidite)Ir Complexes-Resting States, Synthesis, and Characterization of Catalytically Active (π-Allyl)Ir Complexes

A simple method for the synthesis of Ir complexes of cyclo-metallated phosphoramidite ligands was reported. In a dry Schienk flask under argon, a solution of [{Ir(cod)Cl}2] and L2 in absolute THF was stirred for 20 mm and then AgClO4 and isomerically pure trans-crotyl methyl carbonate were added. After 4 h precipitated AgCl was filtered off. The solvent and excess carbonate were removed in vacuo. The spectroscopically pure complex K4 b was obtained as yellow-brown, amorphous, air-stable solid. It was possible to subject the complex to chromatography without inert gas and thereby to remove excess carbonate. The complex K4b was obtained as yellowish powder. DFT calculations were carried out for the cyclometallated complexes K4, Ar=Ph, the binaphthyl group was replaced by a biphenyl group and cod by cot. The results demonstrate that the relative rates of the steps and the stabilities of the intermediates of the catalytic cycle vary considerably.