Synthesis of Heterodimetallic Iridium–Palladium Complexes Containing Two Axes of Chirality: Study of Sequential Catalytic Properties

Abstract

The reaction of [Cp*Cl2Ir(triazolium-ylidene)]BF4 (Cp* = pentamethylcyclopentadienyl) with chiral orthometalated palladium dimers results in facile bridge splitting to afford heterodimetallic Ir–Pd* complexes. The structural characteristics of these complexes show the presence of different isomers as a consequence of hindered rotation about the M–Ccarbene bond (M = Ir/Pd). The heterodimetallic complexes contain two axes of chirality related to each metal. The crystal structure of one heterodimetallic iridium–palladium complex derived from the chiral N,N-dimethylbenzylamine ligand is described and contains two of the rotamers. The Ir/Pd* complexes have been tested in a sequence of two catalytic reactions, which implies the isomerization and asymmetric hydrophosphination of 1,3-diphenylpropargyl alcohol. All the catalysts show high activity in the overall reaction process and excellent regioselectivity, although the enantioselectivities were low.