STRUCTURE OF TRISODIUM HEXAFLUOROMANGANATE(III)

Na3MnF6, M(r) = 237.90, monoclinic, P2(1)/n, a = 5.4709 (9), b = 5.6830 (6), c = 8.0734 (12) angstrom, beta = 88.964 (7)-degrees, V = 250.97 (6) angstrom 3, Z = 2, D(x) = 3.15 g cm-3, lambda(Mo K-alpha) = 0.7107 angstrom, mu = 27.6 cm-1, F(000) = 224, T = 293 K, R = 0.0152, wR = 0.0144 for 550 unique reflections [F(o) > 3-sigma(F(o))]. The structure is isostructural with that of the cryolite Na3AlF6 and shows the weakest static Jahn-Teller distortion known to date for [MnF6]3- octahedra [d(Mn F) axial 2.0176 (8), mean equatorial 1.880 (1) angstrom]. The ordering of the elongated octahedra is ferrodistortive. Of the Na ions, one third have octahedral and the remainder have bicapped trigonal prismatic eight coordination.