Hydrothermal synthesis and crystal structure of two new hydrated alkaline earth metal borates Sr _3B _6O _(11)(OH) _2 and Ba _3B _6O _(11)(OH) _2

摘要

Two new hydrated borates Sr _3B _6O _(11)(OH) _2 (1) and Ba _3B _6O _(11)(OH) _2 (2) were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by IR, powder XRD, and DSC/TGA. Compound 1 crystallizes in the triclinic space group P-1 with unit cell parameters of a = 6.6275(13) ?, b = 6.6706(13) ?, c = 11.393(2) ?, α = 91.06(3)°, α = 94.50(3)°, and β = 93.12(3)°, while compound 2 crystallizes in the noncentrosymmetric monoclinic space group Pc with a = 6.958(14) ?, b = 7.024(14) ?, c = 11.346(2) ?, and α = 90.10(3)°. In spite of the differences in symmetry and packing of the borate chains, both structures consist of the same fundamental building block (FBB) of a [B _6O _(11)(OH) _2] ~(-6) unit and three unique alkaline earth metal atoms.