Ni[B2(SO4)4] and Co[B2(SO4)4]: Unveiling Systematic Trends in Phyllosilicate Analogue Borosulfates

Borosulfates are compounds analogous to silicates, with heteropolyanionic subunits of vertex‐linked (SO4)‐ and (BO4)‐tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. This is particularly true for representatives with phyllosilicate and tectosilicate analogue anionic substructures. Herein, we present Ni[B2(SO4)4] and Co[B2(SO4)4], two new borosulfates with phyllosilicate analogue topology. While the anionic subunits of both structures are homeotypic, the positions of the charge compensating cations differ significantly: NiII is located between the borosulfate layers, while CoII—in contrast—is embedded within the layer. Detailed analysis of these two structures based on single‐crystal X‐ray diffraction, magnetochemical investigations, X‐ray photoelectron spectroscopy, and quantum chemical calculations, unveiled the reasons for this finding. By in silico comparison with other divalent borosulfates, we uncovered systematic trends for phyllosilicate analogues leading to the prediction of new species.
In layers: Ni[B2(SO4)4] and Co[B2(SO4)4] were obtained from solvothermal reactions in sulfuric acid and SO3. Single‐crystal X‐ray diffraction reveals a layer‐like arrangement of (SO4)‐ and (BO4)‐tetrahedra—analogous to the structure of phyllosilicates—with distinct positions of the charge balancing cation: Ni prefers a position between the layers, whereas Co within. Combined experimental and theoretical studies reveal systematic trends and give hints to new phyllosilicate analogue materials.