SYNTHESIS OF PLANAR-SHEET GRAPHITE FLUORIDES USING FLUOROMETALLATE SALTS OF TRANSITION-METALS IN ANHYDROUS HYDROGEN-FLUORIDE

Planar-sheet graphite fluorides. C(x)F. are prepared at ambient temperature by the reaction of graphite with the transition fluorometallates K2MnF6 and K2NiF6 in anhydrous hydrogen fluoride (AHF). In the case of K2MnF6, this represents the first chemical route to graphite fluorides without use of elemental fluorine. For each reagent. the net reactions are identified by stoichiometry and X-ray diffraction of the solid products. The graphite fluorides generated at the oxidation limit have stoichiometries close to C6F and C2F for the Mn4+ and Ni4+ fluorometallates, respectively. Na3FeF6 will also oxidize graphite to C(x)F in AHF, although homogeneous products were not obtained due to rapid solvolysis of the fluorometallate. CoF3 and KF react in AHF to release F2. C(x)F is produced when graphite is reacted with this oxidizing combination. The reactions and oxidation limits are discussed in terms of a thermodynamic model for graphite intercalation. A synthetic strategy for the preparation of planar-sheet graphite fluorides in organic solvents is proposed.