Phosphinophosphoranes: Mixed-Valent Phosphorus Compounds with Ambiphilic Properties

Herein, we present a simple synthesis of mixed-valent phosphinophosphoranes bearing three-and five-coordinate phosphorus centers. Compounds with phosphorus-phosphorus bonds were synthesized via a reaction of lithium phosphides RR ' PLi with cat2PCl (cat = catecholate), whereas derivatives with methylene-linked phosphorus centers were obtained via a reaction of phosphanylmethanides RR ' CH2Li with cat2PCl. The presence of accessible lone-pair electrons on the P-phosphanyl atom of phosphinophosphoranes during the reaction of the title compounds with H3B center dot SMe2, where phosphinophosphorane-borane adducts were formed quantitatively, was confirmed. Furthermore, the Lewis basic and Lewis acidic properties of the phosphinophosphoranes in reactions with phenyl isothiocyanate were tested. Depending on the structure of the starting phosphinophosphorane, phosphinophosphorylation of PhNCS or formation of a five-membered zwitterionic adduct was observed. The structures of the isolated compounds were unambiguously determined by heteronuclear nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction. Moreover, by applying density functional theory calculations, we compared the Lewis basicity and nucleophilicity of diversified trivalent P-centers.

Automated summary

In this study, a simple synthesis method for mixed-valent phosphinophosphoranes was presented, and their properties were investigated. By reacting different ligands and reagents, phosphinophosphoranes with different structures could be obtained, allowing for the control of their properties. Through experiments and calculations, the properties of various compounds were compared.