Synthesis and Crystal Structure of the Iron Borate Fe2B2O5

Fe2B2O5, synthesized under mild high-pressure / high-temperature conditions of 3 GPa and 960 ◦C, possesses a structure isotypic to the triclinic pyroborates M2B2O5 withM = Mg, Mn, Co, and Cd. Although the parameter pressure is not essential to the synthesis of Fe2B2O5, the specific conditions enhance the crystallinity of the product. Therefore, the crystal structure of the iron pyroborate Fe2B2O5 could be determined via single crystal diffraction data [space group P1̄ (Z = 4) with the parameters a = 323.1(1), b = 615.7(2), c = 935.5(2) pm, α = 104.70(3), β = 90.82(3), γ = 91.70(3)◦ , V = 0.1799(1) nm3, R1 = 0.0409, and wR2 = 0.0766 (all data)]. The structure is built up from layers of isolated pyroborate units ([B2O5]4−), which are composed of two corner-sharing BO3 triangles. These pyroborate layers serve to bridge 4×1 ribbons of edge-sharing FeO6 octahedra by both edgeand corner-sharing.