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.