Structural proof of a [C–F–C]+ ﬂuoronium cation
Organic ﬂuoronium ions can be described as positively charged molecules in which the most electronegative and least polarizable element ﬂuorine engages in two partially covalent bonding interactions to two carbon centers. While recent solvolysis experiments and NMR spectroscopic studies on a metastable [C–F–C]+ ﬂuoronium ion strongly support the divalent ﬂuoronium structure over the alternative rapidly equilibrating classical carbocation, the model system has, to date, eluded crystallographic analysis to conﬁrm this phenomenon in the solid state. Herein, we report the single crystal structure of a symmetrical [C–F–C]+ ﬂuoronium cation. Besides its synthesis and crystallographic characterization as the [Sb2F11]− salt, vibrational spectra are discussed and a detailed analysis concerning the nature of the bonding situation in this ﬂuoronium ion and its heavier halonium homologues is performed, which provides detailed insights on this molecular structure.