No abstract

Red single crystals of Eu2O2Br were obtained as a by‐product in an attempt to produce large quantities of Eu4OBr6 from a reaction mixture of EuBr2, Eu2O3 and sodium in a 10:1:2 molar ratio. The crystal structure (monoclinic, I2/m (no. 12), Z = 4, a = 955.2(2), b = 403.01(8), c = 1119.0(3) pm, β = 105.78(3)°, R1(all) = 0.0305) contains {Eu4O} tetrahedra connected to two kinds of chains which combine to corrugated layers [Eu2O2]+ and sheathe likewise corrugated layers of Br− ions.

Black single crystals of tetrasamarium(II)-oxide-hexabromide, Sm 4 OBr 6 , were obtained from a reaction of SmBr 3 , Sm 2 O 3 and Na in a sealed tantalum container at 750°C. Sm 4 OBr 6 crystallizes in the hexagonal space group P6 3 mc (Z ϭ 2, a ϭ 985.89(9), c ϭ 753.50(6) pm, R ϭ 0.035 for all data) as do all M 4 OX 6 type oxide halides with M ϭ Ca,Sr,Ba,Eu,Sm,Yb and X ϭ Cl,Br,I, as far as they have been obtained. The crystal structure is also the Oxide-halides of the formula type M 4 OX 6 have been obtained for the alkaline-earth elements calcium, strontium, and barium and for the lanthanides samarium, europium, and ytterbium in their divalent state. Only the elements of the triad chlorine, bromine and iodine have been observed as X elements. Of the 18 possible combinations, all chlorides, four out of six iodides and, hitherto, only one bromide, Eu 4 OBr 6 , were obtained as single crystals, in many cases not deliberately, rather as by-products. Table 1 gives an overview.

Metallothermic reductions of LaBr3, LaI3 and CeI3 with barium metal resulted in single crystals of La4ZBr7, M9Z4I16 and BaM4Z2I8 (M = La,Ce) as by‐products, subject to apparently ubiquitous “oxygen” and/or “nitrogen” (= Z) impurities. The crystal structure of La4ZBr7 (1, orthorhombic, Pnma, Z = 4, a = 1212.4(1), b = 1404.8(2), c = 804.7(1) pm, R1 = 0.0358 for I>2σI with N:O = 0.91:0.09) is determined by isolated {La4Z} tetrahedra surrounded by and connected through bromide ligands. In the crystal structure of Ce9Z4I16 (2, orthorhombic, Fddd, Z = 8, a = 890.0(1), b = 2264.1(2), c = 4279.5(4) pm, R1 = 0.0262 for I>2σI with N:O = 0.75:0.25), {Ce4Z} tetrahedra are connected to {Ce4/2Z} chains via common edges and further to layers by iodide ligands. The layers are stacked and connected via the ninth cerium atom according to Ce[{Ce4/2Z}I4]4. Similar {La4/2Z} chains and BaI8/4 chains run perpendicularly to each other and are connected via common iodide ions in the crystal structure of BaLa4Z2I8 = Ba2[{La4/2Z}I4]4 (3, monoclinic, C2/c, Z = 4, a = 897.5(1), b = 2162.4(3), c = 1229.3(2), β = 110.32(1)°, R1 = 0.0261 for I>2σI with N:O = 0.54:0.46). The nature of the interstitial Z, oxygen and/or nitrogen, is evaluated.

Red single crystals of Eu 2 OI 2 were obtained from a reaction mixture of barium metal, EuI 2 , Eu 4 OI 6 and some NH 4 I in a tantalum tube at 780/500°C. The crystal structure (orthorhombic, Imcb, Z ϭ 4, a ϭ 648.93 (11), b ϭ 742.85(13), c ϭ 1307.1(3) pm, R1(all) ϭ 0.0605) contains {Eu 4 O} tetrahedra connected via trans-Deutsche Forschungsgemeinschaft, Bonn (Schwerpunktprogramm "Lanthanoid-spezifische Funktionalitäten") and by the State of Nordrhein-Westfalen and the Universität zu Köln.