K4 [BS4 O15 (OH)], Ba[B2 S3 O13 ], and Gd2 [B2 S6 O24 ] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid H[B(HSO4 )4 ] which is subsequently reacted in an open system with anhydrous chlorides of K, Ba, and Gd to the respective borosulfates and a volatile molecule (HCl). Furthermore, protonated borosulfates should be accessible by appropriate stoichiometry of the starting materials, particularly in closed systems, which inhibit deprotonation of H[B(HSO4 )4 ] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (Ba[B2 S3 O13 ] with band-silicate topology and Gd2 [B2 S6 O24 ] with cyclosilicate topology) and the first hydrogen borosulfate K4 [BS4 O15 (OH)].

K 4 [BS 4 O 15 (OH)],B a[B 2 S 3 O 13 ]u nd Gd 2 [B 2 S 6 O 24 ] wurden durche inen neuen Syntheseansatz erhalten. Dabei wurde zunächst die komplexeSäure H[B(HSO 4 ) 4 ]hergestellt; diese wurdea nschließend in einem offenen System mit wasserfreien Chloriden von K, Ba und Gd zu den jeweiligen Borosulfaten und einem flüchtigen Molekül (HCl) umgesetzt. Protonierte Borosulfate sollten ebenfalls zugänglichs ein, indem eine geeignete Stçchiometrie der Startmaterialien eingestellt wird, besonders in geschlossenen Systemen, welchedie Deprotonierung von H[B(HSO 4 ) 4 ]ü ber Kondensation und Dehydratisierung hemmen. Dieser Ansatz führte zur Synthese der ersten Borosulfate zwei-und dreiwertiger Kationen (Ba-[B 2 S 3 O 13 ]und Gd 2 [B 2 S 6 O 24 ]mit Bandsilicat-bzw.Ringsilicat-Topologien) sowied es ersten protonierten Alkalimetallborosulfats (K 4 [BS 4 O 15 (OH)]).

15 (OH)] (I) is prepared by heating a 1:2 molar mixture of HBO 2 and K 2 S 2 O 7 (glass ampoule, 300 C, 60 h). (I) crystallizes in space group I2/a (single crystal XRD) and features non-condensed [B(HSO 4 )(SO 4 ) 3 ] 4super-tetrahedra resembling the topology of the anions of alkali borosulfates. Ba[B 2 S 3 O 13 ] (II) is obtained by heating a mixture of H 3 BO 3 and conc. H 2 SO 4 (280 C, 20 h) followed by the addition of oleum and BaCl 2 and a final heating stage in air (280 C, 60 h). Gd 2 [B 2 S 6 O 24 ] (III) is similarly prepared via heating the mixture of H 2 SO 4 and H 3 BO 3 under N 2 to form H[B(HSO 4 ) 4 ] (Schlenk flask, 201 C, 75 min) followed by the addition of GdCl 3 and oleum in a N 2 counterflow and solvothermal treatment (250 C, 60 h). Compound (II) crystallizes in the space group Pnma (Z = 4, single crystal XRD) and features borosulfate double chains which are described in detail. (III) exhibits a new structure type (space group C2/c, Z = 3) and represents the first cycloborosulfate with four-membered rings with alternating BO 4 and SO 4 tetrahedra arranged in a tetragonal rod packing along (010) with Gd in the vacancies. -(GROSS, P.; KIRCHHAIN, A.; HOEPPE*, H. A.; Angew. Chem., Int. Ed. 55 (2016) 13, 4353-4355, http://dx.