The crystal structures of the M2NaIO6 series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I– with O2(air) to I7+ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali‐metal periodate with the alkaline‐earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P21/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba2NaIO6 contains the first perfectly octahedral [IO6]5– unit reported. The compounds of the ortho‐periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR‐ and Raman‐active vibrations.

In analogy to the synthesis of polycrystalline M 2 NaIO 6 (M = Ca, Sr, Ba) by precipitation in water at 90°C, the title compound was first prepared as a metastable compound. The stable modification of Pb 2 NaIO 6 was obtained by a heat treatment to 400°C followed by cooling to room temperature. The crystal structure was refined from powder diffraction data [space group P2 1 /c (14), a = 5.9040(2), b = 5.7526(2), c = 10.1104(3) Å, β = 125.341(1)°]. On heating, at ca. 125°C, a phase transition to a cubic high temperature modification was observed. The crystal structure was refined from XRD data mea-* Prof. Dr. F. Kubel Fax: +43-1-58801-17199 E-Mail: Frank.Kubel@tuwien.ac.at [a]

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The Periodate-Based Double Perovskites M 2 NaIO 6 (M: Ca, Sr, and Ba). -The title compounds are prepared from mixtures of MF2 (M: Ca, Sr, Ba) and NaI (Pt crucible, 650°C, 18 h, yield given in g). Ba2NaIO6 is also prepared from Ba(OH)2·8H2O and NaIO4 at 650°C (yield >85%). The samples are characterized by powder XRD, SEM, IR, and Raman spectroscopy. The Ba compound crystallizes in the cubic space group Fm3m with Z = 4, whereas the Sr and Ca compounds crystallize in the monoclinic space group P21/c with Z = 2. The crystal structures consists of symmetric (for Ba) or distorted (Sr and Ca) perovskite superstructures. Ba2NaIO6 contains the first perfectly octahedral [IO6] 5unit reported. -(KUBEL*, F.; WANDL, N.; PANTAZI, M.; D'ANNA, V.; HAGEMANN, H.; Z. Anorg. Allg. Chem. 639 (2013) 6, 892-898, http://dx.

The new compound Ba2SrMg4F14 is synthesized by precipitation from an aqueous solution of Ba(OH)2, Sr(OH)2, and Mg(OAc)2 with NH4 followed by heating at 650 °C for 3 h in a Pt crucible.