Multidentate Phosphanyl Phosphinines: Synthesis and Properties

With respect to the well-developed chemistry of pyridines, that of phosphinines is in its infancy. There are still challenges to be overcome with respect to the development of simple syntheses and the application of phosphinine derivatives. Here, we show that sodium phosphinin-2-olate is a valuable building block to prepare multidentate phosphinine ligands, which in turn can be employed for the preparation of metal complexes. These Pd-II and Rh-I complexes were fully characterized, including by NMR spectra and single-crystal X-ray diffraction studies, which clearly demonstrate that molecules R3-xP(O-phosphinine)(x) with one, two, and three phosphinines (x=1, 2, 3) can be tethered to a central phosphorus donor center to give bis-, tris-, and tetradentate ligands.