Borosulfate breaks through

Henning Höppe, together with a team from the University of Augsburg and Albert Ludwigs University Freiburg in Germany, created potassium borosulfate – K5[B(SO4)4]– – by heating potassium sulfate with boric and sulfuric acids. The compound they created comprises a boron atom linked through four oxygen atoms to four sulfate groups and carries a formal 5– charge.

Making such anions where several sulfate groups are bonded together through a central atom is difficult because of the high formal charge on sulfur. Another unusual aspect of the cluster is that, even in the solid state, the structure is made up of isolated anions – interspersed with potassium cations – rather than having several anions linked together to make more extended networks.

The structure was confirmed using powder and single crystal x-ray diffraction, combined with IR and Raman spectroscopies and theoretical calculations. The team now intends to fully investigate the electronic structure and properties of the new material.

The work is published in Angewante Chemie, International Edition (DOI: 10.1002/anie.201109237).