Three Bromides of Lanthanum: LaBr 2 , La 2 Br 5 , and LaBr 3

Colourless LaBr 3 was obtained via the ammonium‐bromide route and in singlecrystalline form by chemical vapour‐phase transport with aluminium tribromide. Black single crystals of LaBr 2 and La 2 Br 5 have been grown from the melts that are obtained by lithium reduction of lanthanum tribromide in sealed tantalum ampoules at 850°C. The crystal structures of the three bromides of lanthanum were refined: LaBr 2 . 2H 2 –MoS 2 type, hexagonal (P6 3 /mmc), a = 409.88(4) pm, c = 1390.0(1) pm, R = R w = 0.092; La 2 Br 5 . Pr 2 I 5 type, monoclinic (P2 1 /m), a = 789.09(6) pm, b = 424.89(4) pm, c = 1342.3(1) pm, β = 91.60(1)º, R = 0.067, R w = 0.055; LaBr 3 . UCl 3 type, hexagonal (P6 3 /m), a = 797.13(4) pm, c = 452.16(4) pm, R = 0.036, R w = 0.032.