The Borosulfates K4[BS4O15(OH)], Ba[B2S3O13], and Gd2[B2S6O24]

K₄BS₄O₁₅(OH)], BaB₂S₃O₁₃], and Gd₂B₂S₆O₂₄] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid HB(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 HB(HSO₄)₄] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (BaB₂S₃O₁₃] with band‐silicate topology and Gd₂B₂S₆O₂₄] with cyclosilicate topology) and the first hydrogen borosulfate K₄BS₄O₁₅(OH)].