Preparation and ESR of phosphorus spiro compounds. Part III

The synthesis of 2,2′‐biphenylenediphenylphosphonium, 2,2′‐biphenylenephenylbenzylphosphonium and 2,2′‐biphenylenephenyl(p‐nitrophenyl)phosphonium salts is described. The related phosphoranyl radicals I, IV and V, generated by electrochemical reduction, are measured by ESR spectroscopy. A similar procedure is followed for the radicals II and III; related phosphonium compounds are described in the literature. The small values of the phosphorus doublet splitting constants are an indication for a tetrahedron (T) like configuration of the phosphorus. The odd electron is delocalized in the aromatic ligands and the five 3‐dorbitals of the phosphorus. It is shown that the spin‐ and odd electron density distribution depends on the electron affinity of the aryl ligands. This is confirmed by quantum chemical calculations.