Using the Lewis Acid Me3Si−F−Al(ORF)3 To Prepare Phosphino‐Phosphonium Cations with the Least‐Coordinating Anion [(RFO)3Al−F−Al(ORF)3]−

By reaction of two equivalents of Me3Si−F−Al(ORF)3 1 with an equimolar amount of PPh2Cl, the salt [Ph2P−PPh2Cl]+[(RFO)3Al−F−Al(ORF)3]- 2 may be prepared smoothly in 91% yield (NMR, XRD). The synthesis of [Ph2P−PPh3]+[(RFO)3Al−F−Al(ORF)3]- 3 is best achieved by a two-step reaction: First, two equivalents of 1 react with one PPh3 to give [Me3Si-PPh3]+[(RFO)3Al−F−Al(ORF)3]- 4 (NMR, XRD), which upon reaction with PPh2Cl yields pure 3 and Me3SiCl (NMR, XRD). Typically, a stoichiometry of two equivalents of 1 with respect to one equivalent of the chloride donor should be used. Else, the residual strong Lewis acidity of the [(RFO)3Al−F−Al(ORF)3]− anion in the presence of the [F−Al(ORF)3]- anion - that forms with less than two equivalents of 1 - leads to further chloride exchange reactions that complicate work up. This route presents the easiest way to introduce the least coordinating [(RFO)3Al−F−Al(ORF)3]- anion into a system. We expect a wide use of this route in all areas, where chloride bond heterolysis in combination with very weakly coordinating anions is advisable. Additionally, we performed calculations on the bond dissociation mechanisms of [R2P−PMe3]+ and the isoelectronic Me2P−SiMe3 and Me2Si−PMe3 in dependence of the solvent's permittivity. These calculations show especially for the neutral reference compounds a heavy influence of the solvent on the dissociation mechanism, which is why we suggest to always investigate these properties in solution instead of gas phase.