The First Bismuth Borosulfates Comprising Oxonium and a Tectosilicate-Analogous Anion

The first bismuth borosulfate (H₃ O)Bi[B(SO₄ )₂ ]₄ is only the second featuring a three-dimensional anion, the first tectosilicate-analogous borosulfate synthesised solvothermally without a precursor (from Bi(NO₃ )₃ ⋅5 H₂ O and B(OH)₃ in oleum); moreover, it is the first comprising two differently charged cations and crystallises in a new structure type in space group I $$ (no. 82) (a=11.857(1), c=8.149(1) Å, 1947 refl., 111 param., wR2=0.037), confirmed by a second harmonic generation (SHG) measurement. The B(SO₄ )₄ supertetrahedra are connected via all four sulfate tetrahedra resulting in a three-dimensional anion with both H₃ O⁺ and Bi³⁺ cations in channels. Additionally, the crystal structure of a further bismuth borosulfate, Bi₂ [B₂ (SO₄ )₆ ], is elucidated crystallising isotypically to the rare-earth borosulfates R₂ [B₂ (SO₄ )₆ ] in space group C2/c (No. 15) (a=13.568(2), b=11.490(2), c=11.106(2) Å, 3127 refl., 155 param., wR2=0.035). Moreover, the optical and thermal properties of both compounds are discussed.