Borosulfates—Synthesis and Structural Chemistry of Silicate Analogue Compounds

Borosulfates are oxoanionic compounds consisting of condensed sulfur‐ and boron‐centered tetrahedra. Hitherto, they were mostly achieved from solvothermal syntheses in SO3‐enriched sulfuric acid, or from reactions with the superacid H[B(HSO4)4]. The crystal structures are very similar to those of the corresponding class of silicates and their substitution variants, especially regarding the typical structural motif of corner‐sharing tetrahedra. However, the borosulfates are supposed to be even more versatile, because (BO3) units might also be part of the anionic network. The following article deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties. Borosulfates are structurally similar to silicates. Their anionic subunits consist of alternating (SO4) and (BO4) tetrahedra forming oligomers, single and multiple chains, layers and extended 3D network structures. The review deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties.