Synthesis and structure of La[B5O8(OH)(H2O)]NO3•2H2O

Boric acid is used as a flux and reactant to synthesize a novel hydrated rare earth polyborate, La[B5O8(OH)(H(2)o)]NO3 center dot 2H(2)O. The structure of the title compound is established by single X-ray diffraction data. It crystallizes in monoclinic structures(P2(1)/n) and consists of a double three-membered ring composed of three BO4 and two BO3 groups as the fundamental building block(FBB). The FBB shares four common oxygen atoms with the the adjacent FBBs producing a borate layer containing nine-membered borate ring window. Lanthanum cations are located around the center of the nine-membered ring. The borate layers are stacked along the b axis and are inter-linked by the La-O bond. Nitrate ions and some water molecules are sandwiched between the borate layers. This study further demonstrates that the low temperature synthesis approach by using molten boric acid as a flux is effective for the syntheses of hydrated rare earth polyborates.