Preparation, Structure, and Properties of V2GeO4F2––Chains of VO4F2 Octahedra in the First V(III) Metallate Fluoride

Powder samples of the new oxide fluoride V2GeO4F2 have been obtained by the reaction of appropriate amounts V2O3, VF3, and GeO2 at 700°C for 18 h in an argon-filled sealed platinum tube. V2GeO4F2 crystallizes in the space group Pnma with a= 9.336(1), b=8.898 (1), and c=4.912 (1) ?. The structure has been refined from X-ray powder diffraction data using the Rietveld method (Rint=5.5% and Rp=9.8%). The structure of V2GeO4F2 exhibits close packed layers of the anions with an ordering of O and F. The characteristic building units are discrete GeO4 tetrahedra with Ge–O distances of 1.75–1.80 ?. The V are coordinated by four O and two F to form VO4F2 octahedra connected via two common edges to give zigzag chains. These chains are linked via corners to form a three-dimensional network. The temperature dependence of the magnetic susceptibility of V2GeO4F2 indicates antiferromagnetic correlations.