Asymmetric synthesis and the coordination chemistry of a P-chiral diphosphine monoxide

The organopalladium complex containing ortho-metalated (R)-(1-(dimethylamino)ethyl)-naphthalene as the chiral auxiliary has been used successfully to promote the asymmetric [4+2] exo-cycloaddition reaction between 1-phenyl-3,4-dimethylphosphole and vinyldiphenylphosphine oxide. The resulting P-chiral phosphanorbornene was obtained as a P–O bidenate chelate on the palladium template. The phosphanorbornene (−)-(L) could be liberated from the palladium template as a highly air-sensitive oil by the treatment of the template complex with aqueous potassium cyanide. Upon recoordination to the Au(I) ion, the diphosphine monoxide coordinated to Au(I) as a monodentate ligand via its tertiary phosphorus donor atom to form the linear complex (+)-[(L–P)AuCl]. The chloro ligand and the pendant PO group in the gold complex showed significant hydrophilicity as they both formed hydrogen bondings to a water molecule. However, the neutral gold complex is not soluble in water.