Manganese(II) Hexafluoroarsenate: Unusually High Coordination of Manganese(II) in a Fluorine Environment

Mn(AsF6)2 was prepared from MnF2 and AsF5 in anhydrous hydrogen fluoride (aHF), and single crystals were grown from the respective solution. The compound crystallizes in the tetragonal space group I42d with a = 750.76(2) pm, c = 1544.44(5) pm, and Z = 4 at 293 K. Due to combined sharing of edges and apexes with AsF6 octahedra, coordination number 8 (Mn−F 4 × 213.0(2) pm and 4 × 241.9(3) pm) is observed for the first time with Mn(II) and fluorine ligands. A second crystalline modification is formed at about 243 K. From susceptibility measurements a magnetic moment of 5.42 μB is derived, but no magnetic ordering is observed above 4 K.