Further New Borosulfates: Synthesis, Crystal Structure, and Vibrational Spectra of A[B(SO4)2] (A = Na, K, NH4) and the Crystal Structures of Li5[B(SO4)4] and NH4[B(S2O7)2]

The reaction of alkali sulfates and boron oxide in oleum yielded the complexes A[B(S2O7)2] (A = Li, Na, K, NH4). This way we obtained the first ammonium‐containing borosulfate and we determined the crystal structure. NH4[B(S2O7)2] [Cc, Z = 8, a = 11.4403(2), b = 14.9439(2) c = 13.8693(2) Å] crystallizes isotyp to K[B(S2O7)2]. Thermal decomposition or treatment in vacuo resulted in compounds with composition A[B(SO4)2]. One‐dimensional chain structures are obtained for A = Na, K, NH4. NH4[B(SO4)2] [P4/ncc, Z = 4, a = 9.1980(1), c = 7.4258(1) Å] and K[B(SO4)2] [P4/ncc, Z = 4, a = 8.9739(3), c = 7.4114(3) Å] are isotyp with H3O[B(SO4)2]. The chains of edge‐sharing “BS4 super tetrahedra” have $\bar{4}$ symmetry. In Na[B(SO4)2] [P2/c, Z = 2, a = 5.434(5), b = 7.570(7) c = 7.766(8) Å, β = 108.56(3)°] the chain is twisted. Li5[B(SO4)4] [P21/c, Z = 4, a = 8.0191(1), b = 10.1211(1) c = 15.0401(2) Å, β = 104.033(1)°] contains isolated pentameric unit and represents a new structure type. Li5[B(SO4)4] was obtained from Li[B(S2O7)2] with additional Li2SO4/SO3. Vibrational spectra of A[B(S2O7)2] (A = Na, K, NH4) are presented and force constants calculated. In all structures BO4 and SO4 tetrahedra are connected by common apices forming BS4 super tetrahedra.