Synthesis and Characterization of Manganese Tetrafluoride β-MnF4

Abstract

The crystal structure of β-MnF4 has finally been elucidated. It crystallizes in the non-centrosymmetric space group R3c, no. 161, hR360, with the lattice parameters a = 19.390(3), c = 12.940(3) Å, V = 4213.3(14) Å3, Z = 72, T = 100 K. It is a 4a × 4a superstructure of the VF3 (FeF3) structure type. The Mn atoms are coordinated octahedron-like by F atoms, of which two are bound terminal, while the other act as μ-bridging F atoms to other Mn atoms forming a three-dimensional infinite network structure which can be described by the Niggli formula 3∞[MnF4/2F2/1]. Voids on the metal sites, which are occupied in the VF3 structure, are grouped together in the shape of a “star” with approximate D3h symmetry. We prepared β-MnF4 photochemically according to the literature and obtained a phase-pure powder as evidenced by X-ray diffraction at room temperature. The lattice parameters are a = 19.566(3), c = 12.984(2) Å, V = 4304(1) Å3. IR and Raman spectra recorded on the powder show that β-MnF4 has also been obtained free of moisture, HF, and O2+ containing compounds, however MnF3 is likely present as a magnetic impurity. We observe thermal decomposition of MnF4 to MnF2 and not MnF3.