Synthesis, Crystal Structure and Properties of Na2MnO2

Abstract Na 2 MnO 2 was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Mn 2 O 3 , NaN 3 and NaNO 3 ) were heated in an appropriate regime up to 390 °C and annealed at this temperature for 20 h, in specially designed silver containers. As the most prominent feature, the crystal structure of Na 2 MnO 2 (C2/c, Z = 12, a = 12.5026(9), b = 12.1006(9), c = 6.0939(4) Å, β = 117.94(0)°, 1556 independent reflections, R 1 = 3.83 % (all data)) forms a three dimensional framework polyanion of corner sharing MnO 4 ‐tetrahedra. The connectivity pattern of the tetrahedral building units corresponds to the moganite structure, a rare SiO 2 modification. According to measurements of the magnetic susceptibility in the temperature range from 2 to 750 K, Na 2 MnO 2 shows antiferromagnetic ordering below 250 K. Evaluation of the high temperature data employing the Curie‐Weiss law revealed a magnetic moment of μ eff = 5.93 μ B , confirming the presence of divalent manganese.