Contributions to hydrogen-fluoride crystal chemistry

Abstract

A series of systems in which hydrogen fluoride is combined with another potential proton or fluoride-ion donor or acceptor have been studied in this laboratory [1] with regard to the formation and characterization of crystalline adducts at ambient or sufficiently reduced temperatures. The main experimental methods employed are difference thermal analysis and X-ray powder diffraction for investigating the respective melting diagrams, as well as single-crystal growth and diffractometry for structure determination. Most of the adducts obtained so far are ionic with the HF component present as complex anions [H n−1F n] −. Others were found to contain fluoronium cations [H n+1F n] +. The anions and cations, with n up to eight and six, respectively, are formed by very strong FHF hydrogen bonds. Their structures will be surveyed. There are also a few adducts which are molecular, i.e. contain the HF as neutral species only. The work was supported by the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen, the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.