The preparation and structures of the alkaline earth iron oxyhalides

Synthesis and Structure of Cobalt (II) Oxide Halides—Sr2CoO2X2 (X=Cl, Br)

“…The search for new layered materials has also led to the development of mixed anion systems, such as oxide carbonates (2), oxide borates (3) and oxide halides (4). For the latter class of compounds this has resulted in a wide range of complex copper oxide halide superconductors, such as (Ca,Na) 2 CuO 2 Br 2 with a T c ¼ 24 K (5), developed from the oxychloride Sr 2 CuO 2 Cl 2 first reported by Grande and M .…”

On the Symmetry of the n=1 Ruddlesden-Popper Phase Ca2FeO3Cl

“…This indicates that Ca2 fits less well in its void compared with Ca1 and is subject to a tensional stress. A first structural characterization of Ca 2 FeO 3 Cl has been given by ACKERMANN (1991). Although the basic structural features were the same as in the present paper, it was suggested that the oxychloride crystallizes in the acentric space group P4.…”

“…The combination between the diffraction symmetry and the systematic absences implicates space group type P4/nmm. However, there are two further indications that suspicion has to be attached to a structure model in P4: (I) A careful analysis of the atomic coordinates given by ACKERMANN (1991) shows, that after shifting the origin by [0.25 0.25 0.209] six pairs of atoms can be found which are independent in the description in P4, but are symmetrically equivalent in P4/nmm. The shifts in the positional coordinates necessary to achieve the higher symmetry are less then 0.1 Å for all atoms.…”

“…Examples are CaLaFeO 4 (NGUYEN- TRUTH-DINH et al 1980) or SrLaFeO 4 (SOUBEYROUX et al 1980), crystallizing in the space group I4/mmm which corresponds to the maximal topological symmetry for a RP-phase with n = 1. A substitution of 25% of the oxygen atoms by chlorine or bromine results in a symmetry reduction within the tetragonal crystal system (space group P4) as described by ACKERMANN (1991) for the oxyhalides Ca 2 FeO 3 Cl, Sr 2 FeO 3 Cl and Sr 2 FeO 3 Br. In the course of our own investigations we observed the structural symmetry P4/nmm for Ca 2 FeO 3 Cl which contradicts the findings of the previous study.…”

Ca4Fe3−Mn O8−Cl2: A new n=3 Ruddlesden–Popper oxychloride

“…Up to now, two manganese-containing oxyhalides have been prepared: Sr 2 MnO 3 Cl, Sr 4 Mn 3 O 7.56 Cl 2 [13,14], with the formal valence states $ 3+ . In addition to manganites, only a few transition metal RP oxyhalides in a single valence state (Cu 2 + , Co 2 + , Co 3 + or Fe 3 + ) are reported [15][16][17][18][19][20][21][22][23]. We successfully synthesized by the flux method, a new series of RP-Mn-oxychloride single crystals: in a ratio of 4:x:3À x (0rx r3; 0.1-0.2 g of the precursor and 2-3 g CaCl 2 -2H 2 O (Aldrich, 499.0%) was placed in a 5 mL Al 2 O 3 crucible.…”