Syntheses and Crystal Structures of the Novel Ternary Thioborates Na3BS3, K3BS3, and Rb3BS3

The orthothioborates Na3BS3, K3BS3 and Rb3BS3 were prepared from the metal sulfides, amorphous boron and sulfur in solid state reactions at temperatures between 923 and 973 K. In a systematic study on the structural cation influence on this type of ternary compounds, the crystal structures were determined by single crystal X-ray diffraction experiments. Na3BS3 crystallizes in the monoclinic space group C2/c (No. 15) with a = 11.853(14) Å, b = 6.664(10) Å, c = 8.406(10) Å, β = 118.18(2)° and Z = 4. K3BS3 and Rb3BS3 are monoclinic, space group P21/c (No. 14) with a = 10.061(3) Å, b = 6.210(2) Å, c = 12.538(3) Å, β = 112.97(2) and a = 10.215(3) Å, b = 6.407(1) Å, c = 13.069(6) Å, β = 103.64(5)°, Z = 4. The potassium and rubidium compounds are not isotypic. All three compounds contain isolated [BS3]3– anions with boron in a trigonal-planar coordination. The sodium cations in Na3BS3 are located between layers of orthothioborate anions, in the case of K3BS3 and Rb3BS3 stacks of [BS3]3– entities are connected via the corresponding cations. X-ray powder patterns were measured and compared to calculated ones obtained from single crystal X-ray structure determinations.