HEXAFLUOROARSENATES OF GRAPHITE FROM ITS INTERACTION WITH ASF5,ASF5+F2, AND O2ASF6, AND THE STRUCTURE OF C14ASF6

The F:As molar ratio for the vacuum-stable products obtained following treatment of graphite, at room temperature, with (1) AsF5, (2) AsF5 F2, and (3) O2AsF6, has been established to be 6. X-Ray absorption sp ectra, in the arsenic-K pre-absorption edge region, indicate that the guest species in the vacuum-stable products via route (1) is AsF6-. Ro ute (1) gives mixtures of stage-one and -two salts whereas (2) and (3) readily yield stage-one materials. This is attributed to the greater oxidizing potential of the reagents in (2) and (3). The volatiles from route (1) are AsF5 and AsF3, and from (2) AsF5. The c-axis repeat dis tance (I(c)) of the vacuum-stable hexafluoroarsenates of formula C14nA sF6 (where n is the stage) is ca. 7.6 + 3.35(n - 1) angstrom. X-Ray po wder diffraction data for C14AsF6 (I(c) almost-equal-to 7.6 angstrom) indicate that the fluoride ligands of AsF6- are nestled in contiguous three-fold sets of carbon atom hexagons of the graphite. This requires a staggering of the enclosing carbon layers. Adjacent pairs of carbon atom sheets contain assemblies of AsF6- of short range order. The ord ered anion arrangement is that of closest packing for nestled AsF6-. A side from the restriction imposed by AsF6- nestling, the carbon layers are randomly stacked. In cases where the graphite galleries are riche r in arsenic fluoride guests (C(x)AsF(y); 8 less-than-or-equal-to x < 14, 5 less-than-or-equal-to y less-than-or-equal-to 6), the I(c) dista nces are larger (ca. 8.0 angstrom) and the enclosing carbon layers are eclipsed.