Syntheses and Crystal Structures of Two New Hydrated Borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]×1.5H2O.

Abstract Two new hydrated borates, Zn 8 [(BO 3 ) 3 O 2 (OH) 3 ] and Pb[B 5 O 8 (OH)]·1.5H 2 O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn 8 [(BO 3 ) 3 O 2 (OH) 3 ] crystallizes in a non-centrosymmetric space group R 32 with a =8.006(2) A, c =17.751(2) A, Z =3 and Pb[B 5 O 8 (OH)]·1.5H 2 O in a triclinic space group P 1¯ with a =6.656(2) A, b =6.714(2) A, c =10.701(2) A, α =99.07(2)°, β =93.67(2)°, γ =118.87(1)°, Z =2. Zn 8 [(BO 3 ) 3 O 2 (OH) 3 ] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons ∞ 1 [Zn 8 O 15 (OH) 3 ] 17− that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional ∞ 3 [Zn 8 O 11 (OH) 3 ] 9− framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B 5 O 8 (OH)]·1.5H 2 O is a layered compound containing double ring [B 5 O 8 (OH)] 2− building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center -related layers are stacked along the c -axis and held together by interlayer Pb 2+ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO 3 and OH groups in Zn 8 [(BO 3 ) 3 O 2 (OH) 3 ], and BO 3 , BO 4 , OH groups as well as guest water molecules in Pb[B 5 O 8 (OH)]·1.5H 2 O.