A new P3N ligand for Pd-catalyzed cross-couplings in water

A new "P3N" ligand, (n-Bu₂N)₃P, derived from PCl₃ and three equivalents of n-Bu₂NH is reported. When complexed to palladium, it readily participates in homogeneous (copper-free) Heck-Cassar-Sonogashira and Suzuki-Miyaura couplings. Reliance on relatively low loadings of Pd is documented under aqueous micellar conditions; i.e., in water containing micelles using the well-established and inexpensive anionic surfactant SDS. Comparisons are shown with several commonly used, representative ligands which, by contrast, are made typically in a number of steps that involve environmentally egregious conditions, and can typically be quite expensive. These issues can now be avoided for these very important reactions using this P3N ligand. Quantum calculations showed the conformational, steric, and electronic nature of P3N ligands and the energetics of their binding to Pd.