Synthesis of Heteroleptic Phosphorus(I) Cations by P⁺ Transfer

Reported are general synthetic approaches for the syntheses of asymmetrically substituted phosphorus(I) cations by P⁺ transfer from [dppeP]⁺ (dppe = 1,2-bis(diphenylphosphino)ethane). The first method grants access to acyclic derivatives and is accomplished by the sequential substitution of dppe using first a sterically encumbered ligand which cannot form a stable homoleptic complex, followed by a second equivalent of a less sterically demanding ligand. The second method grants access to cyclic derivatives and utilizes asymmetric hybrid phosphine/N-heterocyclic carbene ligands. Interplay between the different ligand types and their stoichiometries relative to those of [dppeP]⁺ also allows for the isolation of symmetrical derivatives with pendant phosphines.