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.
Keywords: bismuth; borosulfate; crystal structure; oxonium; silicate-analogous.
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