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 I4̄2d 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.