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

• Published in: ChemPlusChem (Weinheim, Germany) Germany), 2023-07, Vol.88 (7), p.e202200436-n/a
• Main Authors: Keßler, Mira, Kapiza, Michael, Stammler, Hans‐Georg, Neumann, Beate, Röschenthaler, Gerd‐Volker, Hoge, Berthold
• Format: Article
• Language: English
• Subjects: Anions; hypervalent compounds; P ligands; perfluoroalkyl groups; phosphoranides
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.202200436

Phosphoranides comprising three phosphorus carbon bonds are scarcely represented in the literature. We now utilized tris(pentafluoroethyl)phosphane, P(C2F5)3, and cyanobis(pentafluoroethyl)phosphane, P(C2F5)2(CN), featuring electron withdrawing pentafluoroethyl groups, to synthesize such compounds. Metal fluorides MF (M=Ag, Cs) add to P(C2F5)3 yielding respective M[P(C2F5)3F] salts. Those M[P(C2F5)3F] subsequently suffer a loss of C2F4, furnishing M[P(C2F5)2F2]. The cesium salt decomposes instantaneously when warmed to rt, whereas the silver salt decomposes slowly over several days at rt. Treatment of Ag[P(C2F5)3F] with 2,2’‐bipyridine facilitated the isolation and structural characterization of [Ag(bipy){P(C2F5)3F}]. With P(C2F5)2(CN), AgF reacts under substitution of the cyano group yielding P(C2F5)2F, rather than phosphoranide formation. However, [K(18‐crown‐6)]F adds to P(C2F5)2(CN) furnishing [K(18‐crown‐6)][P(C2F5)2(CN)F]. Its structural characterization was successful, despite its tendency to undergo an exchange of substituents, yielding [K(18‐crown‐6)][P(C2F5)2F2] and presumably [K(18‐crown‐6)][P(C2F5)2(CN)2]. The latter forms an equilibrium with [K(18‐crown‐6)]CN and P(C2F5)2(CN) which lies well on side of the phosphane and cyanide salt. Fluoride addition to P(C2F5)3 and P(C2F5)2(CN) furnished respective [P(C2F5)3F]− and [P(C2F5)2(CN)F]− salts, featuring the unusual structural motif of small, open‐chained phosphoranides with three phosphorus carbon bonds. This work reports upon the formation and decomposition of Cs[P(C2F5)3F] and Ag[P(C2F5)3F], the solid‐state structures of [Ag(bipy){P(C2F5)3F}] and [K(18‐crown‐6)][P(C2F5)2(CN)F], and the stability of [K(18‐crown‐6)][P(C2F5)2(CN)F] as well as [K(18‐crown‐6)][P(C2F5)2(CN)2].