Free Difluorobis(pentafluoroethyl)phosphoranide Ion and Its Ligand Properties

In this contribution, we report on the "free" [P(C₂F₅)₂F₂]^- ion and its ligand properties in transition metal complex chemistry. For this purpose, Ag[P(C₂F₅)₂F₂] was treated with [{(Et₂N)₃P═N}₃P═NHC(CH₃)₃]Cl ([EtP₄H]Cl) to yield [EtP₄H][P(C₂F₅)₂F₂], featuring a weakly coordinating phosphazenium cation. Due to the weak interaction between the cation and anion, the [P(C₂F₅)₂F₂]^- ion meets the so-called pseudo-gas-phase conditions. To determine the Tolman electronic parameter, [EtP₄H][Ni(CO)₃{P(C₂F₅)₂F₂}] was prepared from [EtP₄H][P(C₂F₅)₂F₂] and [Ni(CO)₄], facilitating the classification of the P(C₂F₅)₂F₂ moiety as a moderately π-acidic ligand. By treatment of [EtP₄H][P(C₂F₅)₂F₂] with [AuCl(tht)], the neutral tetrahydrothiophene ligand was substituted by the phosphoranide ion, yielding [EtP₄H][AuCl{P(C₂F₅)₂F₂}]. When Ag[P(C₂F₅)₂F₂] was treated with [AuCl(tht)], on the other hand, the chloride was substituted. Transmetalation reactions of this type proved to be an efficient transfer method of the P(C₂F₅)₂F₂ moiety, as further demonstrated by the reactions of Ag[P(C₂F₅)₂F₂] with [FeCl(CO)₂Cp], [FeCl(CO)₂Cp*], and [PdCl₂(NCMe)₂]. Surprisingly, P(C₂F₅)₂F demonstrated fluorinating abilities toward [FeCl(CO)₂Cp], [FeCl(CO)₂Cp*], [AuCl(tht)], and [PdCl₂(NCMe)₂]. Apparently, fluorido transition metal complexes were generated in situ under the formation of P(C₂F₅)₂Cl. The fluorido iron and palladium complexes transfer their fluoride ions onto P(C₂F₅)₂F, yielding the respective phosphoranido complexes, featuring the P(C₂F₅)₂F₂ moiety.