Syntheses and crystal structures of two pentaborates, Na3CaB5O10 and Na3MgB5O10

Two ternary borates, Na3CaB5O10 and Na3MgB5O10, have been prepared by solid-state reactions at temperature below 750 °C. Single-crystal X-ray structural analyses showed that Na3CaB5O10 crystallizes in the triclinic space group P1¯ with a = 7.4403(6) Å, b = 9.7530(10) Å, c = 12.9289(9) Å, α = 90.972(7)°, β = 90.073(7)°, γ = 109.656(6)°, Z = 4 and Na3MgB5O10 in the orthorhombic group Pbca with a = 7.838(1) Å, b = 12.288(1) Å, c = 18.180(2) Å, Z = 8. Na3CaB5O10 has a superstructure, with the cell volume being two times of that reported previously. The crystal structure consists of discrete [B5O10]5− anions separated by six-coordinated Ca2+ as well as five-, six- and seven-coordinated Na+ cations. Na3MgB5O10 contains [B5O10]5− groups that are bridged by MgO4 tetrahedra through common O atoms to form 2D [MgB5O10]3−∞2 layers, with Na+ cations situated between and within the layers. The IR spectra further confirmed the presence of BO3 and BO4 groups in both compounds.

Graphical abstractNa3CaB5O10 has a superstructure, with the cell volume being two times of that reported previously. The crystal structure consists of discrete [B5O10]5− anions separated by six-coordinated Ca2+ as well as five-, six- and seven-coordinated Na+ cations. Na3MgB5O10 contains [B5O10]5− groups that are bridged by MgO4 tetrahedra through common O atoms to form 2D [MgB5O10]3−∞2 layers, with Na+ cations situated between and within the layers.Figure optionsDownload full-size imageDownload as PowerPoint slide