Mössbauer Spectroscopy on Antimony Borosulfates Reveals Weak Coordination Behavior

With M III M I [B(SO 4 ) 2 ] 4 (M III = Bi 3+ , Sb 3+ , Lu 3+ ; M I = H 3 O + , NO 2 + , Li + , Na + , K + , Rb + , Cs + ), we recently described the first modular system within borosulfate chemistry comprising a three‐dimensional anion. Herein, we shed light on the respective series of antimony compounds SbX[B(SO 4 ) 2 ] 4 (X = Li + , Na + , K + , Rb + , Cs + , Ag + , Tl + , NO + , NH 4 + ). While maintaining the same anionic topology, the compounds crystallize in the space groups I (no. 82), P (no. 81), and C 2 (no. 5) and are strongly influenced by the lone pair of antimony as well as the size of the monovalent cations. In the course of this investigation SbX[B 4 O 2 (SO 4 ) 6 ] (X = Li + , Na + ) were discovered. This borosulfate with a one‐dimensional anion comprising B─O─B bridges crystallizes in the space group Pnma (no. 62) and features a new structure type. 121 Sb Mössbauer spectra revealed negative isomer shifts of almost −22 mm·s −1 not observed before and hinting towards a very weak coordination behavior of the borosulfate anion. The spectra are confirmed by DFT calculations. Furthermore, single crystal X‐ray diffraction, infrared spectroscopy, thermal analysis, and temperature programmed X‐ray diffraction experiments were carried out.