Syntheses and crystal structures of two new bismuth hydroxyl borates containing [Bi2O2]2+ layers: Bi2O2[B3O5(OH)] and Bi2O2[BO2(OH)].

Two new bismuth hydroxyl borates, Bi(2)O(2)[B(3)O(5)(OH)] (I) and Bi(2)O(2)[BO(2)(OH)] (II), have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal and powder X-ray diffraction data, respectively. Compound I crystallizes in the orthorhombic space group Pbca with the lattice constants of a = 6.0268(3) Å, b = 11.3635(6) Å, and c = 19.348(1) Å. Compound II crystallizes in the monoclinic space group Cm with the lattice constants of a = 5.4676(6) Å, b = 14.6643(5) Å, c = 3.9058(1) Å, and β = 135.587(6)°. The borate fundamental building block (FBB) in I is a three-ring unit B(3)O(6)(OH), which connects one by one via sharing corners, forming an infinite zigzag chain along the a direction. The borate chains are further linked by hydrogen bonds, showing as a borate layer within the ab plane. The FBB in II is an isolated BO(2)(OH) triangle, which links to two neighboring FBBs by strong hydrogen bonds, resulting in a borate chain along the a direction. Both compounds contain Bi(2)O(2) layers, and the Bi(2)O(2) layers combine with the corresponding borate layers alternatively, forming the whole structures. These two new bismuth borates are the first ones containing Bi(2)O(2) layers in borates. The appearance of Bi(2)O(2)[BO(2)(OH)] (II) completes the series of compounds Bi(2)O(2)[BO(2)(OH)], Bi(2)O(2)CO(3), and Bi(2)O(2)[NO(3)(OH)] and the formation of Bi(2)O(2)[B(3)O(5)(OH)] provides another example in demonstrating the polymerization tendency of borate groups.