SYNTHESIS, STRUCTURAL AND PHYSICAL CHARACTERIZATIONS OF TRANSITION-METAL FLUORIDE GICS

Intercalation of d-metal fluorides into graphite has been investigated using the anhydrous HF route. This method has been applied in particular to Rh-, Ir-, and Au fluroides. Various stages are obtained depending on the starting host graphite and on the fluoride-to-graphite molar ratio. For CxAuFy crystal precession photographs show the presence of two hexagonal lattices corresponding to the intercalates. XANES and EXAFS investigations of stage-2 CxAuFy confirm that Au(III) keeps its square planar configuration during the intercalation as only four nearest fluorine neighbors are detected leading to Au-F = 2.00 and 2.08 angstrom distances. In the NG-based sample, a further distance corresponding to Au-Au = 2.94 angstrom could be accounted for by the presence of square planar AuF4 entities sharing one edge to form Au2F6 dimers. The dimensions of these groups can be inscribed in one of the observed intercalate sublattices. The XPS spectra have confirmed oxidation state III of intercalated Rh. The F 1s envelope has been correlated to the nature of the different types of fluoride ions involved in the structure.