Triorganylphosphoranides: Realization of an Unusual Structural Motif Utilizing Electron Withdrawing Pentafluoroethyl Groups.

Phosphoranides comprising three phosphorus carbon bonds are scarcely represented in the literature. We now utilized tris(pentafluoroethyl)phosphane, P(C2 F5 )3 , and cyanobis(pentafluoroethyl)phosphane, P(C2 F5 )2 (CN), featuring electron withdrawing pentafluoroethyl groups, to synthesize such compounds. Metal fluorides MF (M=Ag, Cs) add to P(C2 F5 )3 yielding respective M[P(C2 F5 )3 F] salts. Those M[P(C2 F5 )3 F] subsequently suffer a loss of C2 F4 , furnishing M[P(C2 F5 )2 F2 ]. The cesium salt decomposes instantaneously when warmed to rt, whereas the silver salt decomposes slowly over several days at rt. Treatment of Ag[P(C2 F5 )3 F] with 2,2'-bipyridine facilitated the isolation and structural characterization of [Ag(bipy){P(C2 F5 )3 F}]. With P(C2 F5 )2 (CN), AgF reacts under substitution of the cyano group yielding P(C2 F5 )2 F, rather than phosphoranide formation. However, [K(18-crown-6)]F adds to P(C2 F5 )2 (CN) furnishing [K(18-crown-6)][P(C2 F5 )2 (CN)F]. Its structural characterization was successful, despite its tendency to undergo an exchange of substituents, yielding [K(18-crown-6)][P(C2 F5 )2 F2 ] and presumably [K(18-crown-6)][P(C2 F5 )2 (CN)2 ]. The latter forms an equilibrium with [K(18-crown-6)]CN and P(C2 F5 )2 (CN) which lies well on side of the phosphane and cyanide salt.