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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.

Identification of an iridium-containing compound with a formal oxidation state of IX

The concept of formal oxidation states is fundamental to our understanding of general chemistry and is enshrined in the periodic table that groups elements principally by atomic number and electron configuration. The preparation and characterization of compounds containing elements with unusual oxidation states is of therefore of great interest to inorganic chemists. The highest experimentally known formal oxidation state of any chemical element is currently VIII. Here, the authors report the formation and infrared photodissociation spectroscopic identification of the iridium tetroxide cation, [IrO4]+, in which the iridium centre has a formal oxidation state of IX, the highest oxidation state known so far.