Combining CDIF and PDF information in problem solving: Crystal structure of a corrosion deposit, hexaaquairon(II) trifluoromethanesulfonate

The title compound was identified as the major phase in a corrosion deposit by indexing its powder pattern, and locating an isostructural vanadium(II) compound in the NIST Crystal Data Identification File. The identity of the compound was confirmed by a Rietveld refinement. Hexaaquairon(II) trifluoromethanesulfonate crystallizes in the monoclinic space group C2/m, with a=18.6415(14), b=6.9291(5), c=6.5938(5)A, (beta)=104.742(6)°, V=823.68(10)A^3, and Z = 2. The structure consists of alternating layers of octahedral hexaaquairon(II) cations and triflate anions. The cations and anions are linked into layers parallel to the be plane by hydrogen bonds. Each water molecule donates two protons to sulfonate oxygens, and each sulfonate oxygen acts as an acceptor of two protons. A reference powder diffraction pattern is reported.