The Borosulfates K 4 [BS 4 O 15 (OH)], Ba[B 2 S 3 O 13 ], and Gd 2 [B 2 S 6 O 24 ]

K 4 [BS 4 O 15 (OH)], Ba[B 2 S 3 O 13 ], and Gd 2 [B 2 S 6 O 24 ] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid H[B(HSO 4 ) 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(HSO 4 ) 4 ] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (Ba[B 2 S 3 O 13 ] with band‐silicate topology and Gd 2 [B 2 S 6 O 24 ] with cyclosilicate topology) and the first hydrogen borosulfate K 4 [BS 4 O 15 (OH)].