The first mixed-valent europium(II,III) oxide bromide : Eu2O2Br

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, beta = 105.78(3)degrees, R-I(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.