Coexistence of the Perfluorinated Cp* Anion With Oxidizing and Electrophilic Cations

Abstract

The air- and water-stable perfluorinated Cp* [C5(CF3)5]− is presented as a candidate for the vastly underexplored group of weakly coordinating carbanions (WCCAs). Its extreme electron deficiency, combined with the stabilization of the negative charge within an aromatic system, results in a low basicity, yielding a very weak coordination ability. As Cp anions usually possess a strongly pronounced carbanionic character, the perfluorinated Cp* resembles an extraordinary exception for both the WCA and Cp chemistry. However, the coordination ability remains ambivalent due to the substitution lability of many of its complexes, allowing for the formation of unique ligand-WCA switches. Due to the low reactivity, there is a need for new transfer reagents containing the perfluorinated Cp* in combination with reactive cations. Thus, we report the synthesis and complete characterization of [C5(CF3)5]− salts with hydride-accepting [(C6H5)3C]+, valuable Ag(I) reagents, oxidizing [Fe(C5H5)2]+ or [N(p-C6H4Br)3]+ and Brønsted acidic [H(m,m-NC5H3F2)2]+. Notably, these unprecedented ion pairs are exclusively accessible and stabilized by the low coordination affinity and pronounced oxidative resistance of the perfluorinated Cp*.