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Single crystals of Na5ReO6 have been obtained from the reaction of Na2O, rhenium metal and CdO in Ag containers at 550 °C. At 700 °C Na2ReO3 is formed possibly via a topotactic redox reaction of Na5ReO6 with rhenium metal. Here we report the crystal structures of Na2ReO3 and a second modification of Na5ReO6, ex‐situ X‐ray diffraction studies of the reactivity within the system Na / Re / O, selected spectroscopic investigations of the two compounds and Extended‐Hückel calculations of the [Re2O6]4‐ anion, containing a rhenium‐rhenium triple‐bond.

Synthesis and Crystal Structure of Na10[M3O6][MO3] (M = Fe, Mn) with a Remark on the Magnetic Properties Single crystals of Na10[M3O6][MO3] (M = Mn, Fe) may be obtained via a redox reaction of CdO with the respective transition metal in the presence of Na2O and a flux as red single crystals, which are sensitive to moisture. The crystal structure (determined from IPDS data, ${\rm R} {\bar 3}{\rm m}$, Z = 6) contains isolated trigonal aplanar [MO3] units and $^{2}_{\infty}\rm [M_{3}O{6}]$ layers of [MO4] tetrahedra connected via corners to three‐membered rings, which share common edges resulting in the formation of twelve‐membered rings. The statistical occupancy of 21 out of 60 sodium atoms per unit cell is discussed and calculations of the Madelung Part of the Lattice Energy (MAPLE) are given. Furthermore, we report on the magnetic properties of Na10[Mn3O6][MnO3] in close relation to the structural entities.

Inhaltsübersicht. Na 8 [CoO 3 ][SO 4 ] 2 wurde durch Redoxreaktion zwischen metallischem Cobalt und CdO in Anwesenheit von Na 2 SO 4 und Na 2 O bei 550°C (15 d) in Form roter Einkristalle erhalten. Die Kristallstruktur wurde anhand von Einkristalldaten bei 170 K bestimmt (IPDS-Daten, Cmcm, Z ϭ 4, a ϭ 806,88 (9) Abstract. Na 8 [CoO 3 ][SO 4 ] 2 has been obtained from a redox reaction between cobalt metal and CdO in the presence of Na 2 SO 4 and Na 2 O at 550°C (15 d) as red single crystals. The structure has been determined from single crystal data (IPDS-data, T ϭ 170 K, Cmcm, Z ϭ 4, a ϭ 806.88(9) pm, b ϭ 2232.1(3) pm, c ϭ 705.97 (9) pm, R all ϭ 0.047). Magnetic properties and spectroscopic investiga-

Synthesis of Na3FeO3, a Ternary Oxoferrate(III) with a Chain Structure Na3FeO3 has been obtained from a redox reaction between CdO and iron metal in the presence of Na2O and Na2CO3 at 650 °C as amber colored transparent single crystals. The crystal structure determination (IPDS data: P21/n, a = 579.9(1) pm, b = 1265.9(2) pm, c = 582.8(1) pm, β = 116.02(2)°, Z = 4, Rall = 0.0576) reveals the presence of  ∞1[FeO2O2/2] zig‐zag‐chains.