La[B_5O_8(OH)(H_2O)]NO_3·2H_2O的合成与结构

Abstract

采用熔融硼酸法合成了一种具有层状结构的新型水合稀土多硼酸盐,La[B_5O_8(OH)(H_2O)]NO_3·2H_2O,并利用单晶X射线衍射技术确定了它的结构.它属于单斜晶系,P21/n空间群.其基本构建单元(fundamental building block,简称FBB)是由三个BO4和两个BO3基团所构成的一个双三元环[B_5O_(10)]基团.结构中每一个FBB通过共顶点氧原子与周围四个同样的单元连接成具有九元环窗口的二维[B_5O_(10)]层,La3+位于九元环中心附近.[B_5O_(10)]层沿着b方向进行堆积,硝酸根离子和结构中部分结晶水分子位于相邻的[B_5O_(10)]层...

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.