Cd[B(SO)] and H[B(SO)] - a phyllosilicate-analogous borosulfate and its homeotypic heteropolyacid.

Borosulfates consist of heteropolyanionic networks of corner-shared (SO)- and (BO)-tetrahedra charge compensated by metal or non-metal cations. The anionic substructures differ significantly, depending on the different branching of the silicate-analogous borosulfate building blocks. However, only one acid has been characterized by single crystal X-ray diffraction so far. Herein, we present H[B(SO)] as the first phyllosilicate analogue representative, together with the homeotypic representative Cd[B(SO)]. The latter can be considered the cadmium salt of the former. Their crystal structures and crystallographic relationship are elucidated. For H[B(SO)], the bonding situation is examined using Hirshfeld-surface analysis. Further, the optical and thermal properties of Cd[B(SO)] are investigated by FTIR and UV-Vis spectroscopy, thermogravimetry, as well as temperature-programmed powder X-ray diffraction.