Abstract
This review deals with the chemistry of phosphinines. As many reviews are available on the syntheses of these derivatives, only the most versatile methods are presented, or the ones giving access to the phosphinines that have been particularly studied. Then, recent results obtained in the coordination chemistry of phosphinines are summarized with an emphasis on their analogy with CO ligands. Indeed, the first studies proved these ligands to be well adapted for the stabilization of electron rich metal centers. Shortly after, highly reduced complexes have been obtained through the reaction of reduced 2,2-biphosphinine dianions with transition metal fragments. Theoretical calculations were performed to establish the oxidation state of the metal in these complexes. On the other hand, the various coordination studies have pointed out that phosphinines become sensitive toward nucleophiles once they are bound to (even slightly) oxidized metal centers. This sensitivity precluded their use in most catalytic processes, but the cases in which they could be used efficiently are presented in this review. Two ways to circumvent this drawback were developed lately. The first method relies on the use of the high electrophilicity of the phosphorus atom of the phosphinine moiety. The ring is readily transformed into phosphacyclohexadienyl anions, which exhibit surprising coordination chemistry and promising behavior in catalysis. Results in this domain are presented. The second method is based on the involvement of the ring, as phosphadiene, into [4+2] Diels Alder type cycloadditions leading to phosphabarrelene derivatives. These ligands also show promising results in catalytic processes. Finally, phosphinines have been used successfully to stabilize gold nanoparticles, which opens a whole new field of applications for these ligands.
Keywords: cycloaddition processes, Electrochemical reduction, biphosphinine ligands, cyclic voltammetry, evaporation induced self assembly (EISA)