The First Mixed‐Valent Europium(II,III) Oxide Bromide: Eu₂O₂Br

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.

Refined Crystal Structure and Idealized Structure of Mixed-Valent Eu4F5(CN2)2: Transition Possible

“…Average Eu–N distances of Eu1, Eu2, Eu3, and Eu4 with their corresponding nitrogen atoms in each case amount to 2.606 Å, 2.749 Å, 2.751 Å, and 2.605 Å, when counting only the next nearest (4, 3, 3, 2) nitrogen neighbors, or to 2.606 Å, 2.950 Å, 2.858 Å, and 3.092 Å, when counting all four nitrogen neighbors in each case as displayed in Figure . The pronounced difference in next neighbor distances of Eu1 on one hand and of Eu2, Eu3, and Eu4 on the other hand is in line with the observed values in other mixed-valent europium compounds, such as Eu 2 O 2 Br …”

“…Mixed-valent europium compounds are well-known from several examples, such as Eu 2 O 2 Br, Na 5 Eu 7 Cl 22 , and Eu 5 F[SiO 4 ] 3 in whose structures separate lattice sites can be addressed to Eu 2+ and Eu 3+ ions, respectively. Compounds like these account for inhomogeneous mixed-valence compounds, where charge fluctuations are considered as being frozen.…”

Anion-Centered Tetrahedra in Inorganic Compounds

“…The layers are separated by chains of corner-sharing [PdO 4 ] 6+ squares as shown in Figure . Layers of the same type have been described by Hammerich et al in the structure of Eu 2 O 2 Br. These authors proposed an alternative description of the layer as based upon condensation of alternating chains of the types shown in Figure a,b (Figure ).…”

“…The chains shown in gray and black are of the types shown in Figure , panels a and b, respectively. Reprinted with permission from ref . Copyright 2006 Wiley-VCH Verlag GmbH & Co KGaA.…”

The Oxonitridoborate Eu5(BO2.51(7)N0.49(7))4 and the Mixed‐Valent Borates Sr3Ln2(BO3)4 (Ln = Ho, Er)

“…Thus, for the latter, shorter coordination distances should be expected. This approach, which basically uses the coordination distances of the europium ions, was introduced by Bärnighausen33 for LiEu 3 O 4 and was later frequently used 34,35…”