Stepwise Functionalization of Two Alkyne Moieties in a Dialkynylphosphine Complex Leading to the Formation of a Bifunctionalized Phosphine Complex Bearing a Stereogenic Center at Phosphorus

Stepwise functionalization of the two alkyne moieties in a dialkynylphosphine complex has been studied. The two alkynyl groups underwent stepwise hydrophosphination and insertion to yield two different substituents on the stereogenic phosphorus. Coordination of the dialkynylphosphine ligand PPh(CCCH3)2 to the ruthenium center generated the complex [Ru(η6-benzene){PPh(CCCH3)2}Cl2]. Removal of one Cl atom by AgPF6 followed by coordination of HPPh2 to ruthenium promoted the hydrophosphination reaction with high stereoselectivity. The hydrophosphination products then underwent insertion into the Pd−C bond of a cyclopalladated complex to give a bimetallic complex bearing a stereogenic phosphorus center with expected substituents. The product contains also a tridentate ligand chelating to palladium, which is believed to have been generated through a proton exchange process aided by palladium. Furthermore, this complex exists as two interconvertable conformations in a ratio of 3:1. The structures of complexes were confirmed by X-ray crystallographic analyses and 2D ROESY NMR studies.