Concerning the crystal structure of BrF3·AuF3

Crystals of the adduct, BrF3·AuF3, are monoclinic, with: a=5.356(4) Å, b=5.766(4) Å, c=8.649(3) Å, β=101.39(4)°, V=261.8(5) Å3, z=2, Dc=4.96 g/cm3. An ordered structure in P21 was found, but is of low precision (R1=0.082) because of crystal deformation. The structure has planar BrF4 units sharing F ligands cis with planar AuF4 groups, each AuF4 being similarly linked to two BrF4. This generates a ribbon, creased at the bridging F along y, the gold on one side of the crease, the bromine on the other. Such ribbons are stacked parallel along y, with nearest neighbors related by twofold screw axes. This sandwiches each AuF4 strip of a ribbon symmetrically between like strips. These contacts between the Au-strips bring up, to each Au-atom, two “non-bridging Au–F ligands” of each of the two neighboring strips, to give eight coordination in F. The bromine side of the creased ribbon is unsymmetrically sandwiched between a screw-axis related relative, and the edge of a Au-containing strip oriented almost perpendicular to it. This brings two non-bridging F of the nearest-strip BrF4 and two non-bridging F of the AuF4 strip into the secondary cordination sphere of the Br atom. Raman spectra of the BrF3·AuF3, molecular BrF3, and polymeric AuF3 suggest that the Br–F and Au–F stretching vibrations of BrF3·AuF3 are shifted slightly from those of the parent BrF3 and AuF3, and indicate some BrF2+AuF4− character.